ci: update docker build workflow and refine frontend theme

Refactor the CI/CD pipeline to use Docker Buildx for more efficient builds and implement automated image tagging and pushing to GHCR.

On the frontend, update the theme system to use a neutral zinc-based dark mode instead of the previous warm dark theme. This includes:
- Updating CSS variables in `globals.css` for a more consistent neutral palette.
- Replacing `ring` color usage with `muted-foreground` in various UI components to align with the new design language.
- Adjusting component backgrounds (e.g., `Header`, `Input`, `WidgetCard`) to use `bg-card` for better visual layering.
- Simplifying component styles and removing unnecessary gradients.

frontend/app/globals.css

@@ -31,28 +31,28 @@
   --font-geist-mono: "Geist Mono", "ui-monospace", "SFMono-Regular", "Roboto Mono", monospace;
 }
 
-/* ── Dark (Rich warm dark — not pure black) ── */
+/* ── Dark (Neutral zinc-dark — no blue, layered depth) ── */
 [data-theme="dark"] {
-  --color-background: #0d0d0d;
-  --color-foreground: #ececec;
-  --color-card: #141414;
-  --color-card-foreground: #ececec;
-  --color-popover: #1a1a1a;
-  --color-popover-foreground: #ececec;
-  --color-primary: #ececec;
-  --color-primary-foreground: #0d0d0d;
-  --color-secondary: #1a1a1a;
-  --color-secondary-foreground: #ececec;
-  --color-muted: #1a1a1a;
-  --color-muted-foreground: #888888;
-  --color-accent: #1a1a1a;
-  --color-accent-foreground: #ececec;
+  --color-background: #09090b;
+  --color-foreground: #e4e4e7;
+  --color-card: #111113;
+  --color-card-foreground: #e4e4e7;
+  --color-popover: #141416;
+  --color-popover-foreground: #e4e4e7;
+  --color-primary: #e4e4e7;
+  --color-primary-foreground: #09090b;
+  --color-secondary: #1a1a1c;
+  --color-secondary-foreground: #e4e4e7;
+  --color-muted: #18181b;
+  --color-muted-foreground: #71717a;
+  --color-accent: #1f1f22;
+  --color-accent-foreground: #e4e4e7;
   --color-destructive: #f43f5e;
-  --color-destructive-foreground: #ececec;
-  --color-border: #262626;
-  --color-ring: #3b82f6;
+  --color-destructive-foreground: #e4e4e7;
+  --color-border: #27272a;
+  --color-ring: #71717a;
   --color-signal: #f43f5e;
-  --color-input: #262626;
+  --color-input: #27272a;
   --color-overlay: #050505;
 }
 
@@ -131,7 +131,7 @@ body {
   opacity: 0.95;
   transform: scale(1.03);
   box-shadow:
-    0px 0px 0px 2px var(--color-ring),
+    0px 0px 0px 2px var(--color-muted-foreground),
     0px 12px 32px rgba(0, 0, 0, 0.25);
   z-index: 50;
 }
@@ -145,7 +145,7 @@ body {
   position: absolute;
   inset: -4px;
   border-radius: inherit;
-  border: 2px dashed var(--color-ring);
+  border: 2px dashed var(--color-muted-foreground);
   opacity: 0.5;
   pointer-events: none;
 }
@@ -154,8 +154,8 @@ body {
 .drop-target-line {
   height: 3px;
   border-radius: 2px;
-  background: var(--color-ring);
-  box-shadow: 0 0 8px var(--color-ring);
+  background: var(--color-muted-foreground);
+  box-shadow: 0 0 8px var(--color-muted-foreground);
   margin: 4px 0;
   animation: pulse-line 1.2s ease-in-out infinite;
 }
@@ -181,14 +181,14 @@ body {
 
 /* ── Colorful badge variants ── */
 .badge-local {
-  background: #0f291e;
+  background: #0f1a15;
   color: #34d399;
 }
 .badge-external {
-  background: #162038;
-  color: #60a5fa;
+  background: #1a1a1c;
+  color: #a1a1aa;
 }
 .badge-custom {
-  background: #231a38;
-  color: #a78bfa;
+  background: #1a1a1c;
+  color: #a1a1aa;
 }

frontend/components/dashboard/dashboard-page.tsx

@@ -68,7 +68,7 @@ function AddAppTile({ onClick }: { onClick: () => void }) {
   return (
     <button
       onClick={onClick}
-      className="service-card group flex aspect-square flex-col items-center justify-center gap-2.5 rounded-[24px] border border-dashed border-border bg-card p-4 transition-all duration-300 hover:-translate-y-1 hover:bg-accent hover:border-ring/40 hover:shadow-border-hover"
+      className="service-card group flex aspect-square flex-col items-center justify-center gap-2.5 rounded-[24px] border border-dashed border-border bg-card p-4 transition-all duration-300 hover:-translate-y-1 hover:bg-accent hover:border-muted-foreground/40 hover:shadow-border-hover"
     >
       <div className="flex h-10 w-10 items-center justify-center rounded-xl bg-secondary transition-colors group-hover:bg-accent">
         <Plus className="h-5 w-5 text-muted-foreground transition-colors group-hover:text-foreground" />
@@ -128,7 +128,7 @@ function DashboardDragOverlay({ activeId, dashboard }: { activeId: string; dashb
 
   if (widget) {
     return (
-      <div className="drag-overlay flex w-56 items-center gap-3 rounded-xl bg-card border border-ring/50 px-4 py-3 shadow-2xl">
+      <div className="drag-overlay flex w-56 items-center gap-3 rounded-xl bg-card border border-muted-foreground/40 px-4 py-3 shadow-2xl">
         <div className="flex h-8 w-8 items-center justify-center rounded-lg bg-accent">
           <GripVertical className="h-4 w-4 text-accent-foreground" />
         </div>
@@ -216,7 +216,7 @@ export default function DashboardPage() {
   if (isLoading) {
     return (
       <div className="flex h-screen flex-col bg-background">
-        <div className="h-14 border-b border-border/50" />
+        <div className="h-14 border-b border-border" />
         <div className="flex flex-1 items-center justify-center">
           <div className="flex flex-col items-center gap-3">
             <div className="flex h-10 w-10 items-center justify-center rounded-xl bg-accent">
@@ -261,7 +261,7 @@ export default function DashboardPage() {
       <main className="mx-auto w-full max-w-6xl flex-1 px-4 py-6">
         {isEmpty ? (
           <div className="flex flex-col items-center justify-center gap-6 py-32">
-            <div className="flex h-20 w-20 items-center justify-center rounded-[24px] bg-gradient-to-br from-secondary to-accent border border-border shadow-border-card">
+            <div className="flex h-20 w-20 items-center justify-center rounded-[24px] bg-secondary border border-border shadow-border-card">
               <LayoutGrid className="h-8 w-8 text-muted-foreground" />
             </div>
             <div className="text-center">
@@ -290,7 +290,7 @@ export default function DashboardPage() {
             <Card className="mb-6">
               <CardHeader className="flex flex-row items-center justify-between pb-3">
                 <div className="flex items-center gap-2">
-                  <div className="h-4 w-0.5 rounded-full bg-ring" />
+                  <div className="h-4 w-0.5 rounded-full bg-muted-foreground" />
                   <CardTitle className="text-xs font-semibold uppercase tracking-wider text-muted-foreground">Widgets</CardTitle>
                 </div>
                 <Button variant="ghost" size="sm" onClick={openAddWidget} className="gap-1.5 text-xs rounded-lg hover:bg-accent">
@@ -310,7 +310,7 @@ export default function DashboardPage() {
                 ) : (
                   <button
                     onClick={openAddWidget}
-                    className="flex w-full items-center justify-center gap-2 rounded-xl border border-dashed border-border bg-secondary/50 p-6 text-sm text-muted-foreground transition-all hover:border-ring/40 hover:bg-accent hover:text-foreground"
+                    className="flex w-full items-center justify-center gap-2 rounded-xl border border-dashed border-border bg-muted p-6 text-sm text-muted-foreground transition-all hover:border-muted-foreground/40 hover:bg-accent hover:text-foreground"
                   >
                     <Plus className="h-4 w-4" /> Add your first widget
                   </button>
@@ -322,7 +322,7 @@ export default function DashboardPage() {
             <Card>
               <CardHeader className="flex flex-row items-center justify-between pb-3">
                 <div className="flex items-center gap-2">
-                  <div className="h-4 w-0.5 rounded-full bg-ring" />
+                  <div className="h-4 w-0.5 rounded-full bg-muted-foreground" />
                   <CardTitle className="text-xs font-semibold uppercase tracking-wider text-muted-foreground">Apps</CardTitle>
                 </div>
                 <div className="flex items-center gap-1">
@@ -370,7 +370,7 @@ export default function DashboardPage() {
                   <div>
                     {groups.length > 0 && (
                       <div className="mb-3 flex items-center gap-2">
-                        <div className="h-4 w-0.5 rounded-full bg-ring" />
+                        <div className="h-4 w-0.5 rounded-full bg-muted-foreground" />
                         <span className="text-xs font-semibold uppercase tracking-wider text-muted-foreground">Ungrouped</span>
                         <span className="text-xs text-muted-foreground font-mono">{ungrouped.length}</span>
                       </div>
@@ -401,7 +401,7 @@ export default function DashboardPage() {
                 {groups.length === 0 && ungrouped.length === 0 && (
                   <button
                     onClick={openAddService}
-                    className="flex w-full items-center justify-center gap-2 rounded-xl border border-dashed border-border bg-secondary/50 p-8 text-sm text-muted-foreground transition-all hover:border-ring/40 hover:bg-accent hover:text-foreground"
+                    className="flex w-full items-center justify-center gap-2 rounded-xl border border-dashed border-border bg-muted p-8 text-sm text-muted-foreground transition-all hover:border-muted-foreground/40 hover:bg-accent hover:text-foreground"
                   >
                     <Plus className="h-4 w-4" /> Add your first app
                   </button>

frontend/components/groups/group-section.tsx

@@ -48,8 +48,8 @@ export function GroupSection({ group, onEditService, onDeleteService, onEditGrou
               className="flex flex-1 items-center gap-2.5 group/title min-w-0"
               onClick={handleToggle}
             >
-              <div className="flex h-7 w-7 items-center justify-center rounded-lg transition-colors bg-accent">
-                <FolderOpen className="h-3.5 w-3.5 text-accent-foreground" />
+              <div className="flex h-7 w-7 items-center justify-center rounded-lg transition-colors bg-secondary">
+                <FolderOpen className="h-3.5 w-3.5 text-secondary-foreground" />
               </div>
               <div className="flex items-center gap-2 min-w-0">
                 <span className="text-sm font-semibold truncate">{group.name}</span>

frontend/components/services/service-card.tsx

@@ -157,8 +157,8 @@ export function ServiceCard({
         )}
         onClick={handleClick}
       >
-        {/* Gradient accent line at top */}
-        <div className="absolute top-0 left-0 right-0 h-[2px] opacity-0 group-hover:opacity-100 transition-opacity bg-ring" />
+        {/* Accent line at top */}
+        <div className="absolute top-0 left-0 right-0 h-[2px] opacity-0 group-hover:opacity-100 transition-opacity bg-muted-foreground" />
 
         <div className="flex h-full flex-col items-center justify-center gap-2.5 p-4">
 

frontend/components/shell/header.tsx

@@ -25,7 +25,7 @@ export function Header({
   const dateStr = now.toLocaleDateString([], { weekday: "short", month: "short", day: "numeric" });
 
   return (
-    <header className="sticky top-0 z-40 w-full border-b border-border bg-background">
+    <header className="sticky top-0 z-40 w-full border-b border-border bg-card">
       <div className="mx-auto flex h-14 max-w-6xl items-center justify-between px-4">
         <div className="flex items-center gap-4">
           <div className="flex items-center gap-2">

frontend/components/ui/input.tsx

@@ -7,7 +7,7 @@ const Input = React.forwardRef<HTMLInputElement, React.InputHTMLAttributes<HTMLI
       <input
         type={type}
         className={cn(
-          "flex h-9 w-full rounded-md border border-border bg-transparent px-3 py-1 text-sm shadow-sm transition-colors file:border-0 file:bg-transparent file:text-sm file:font-medium file:text-foreground placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-50",
+          "flex h-9 w-full rounded-md border border-border bg-card px-3 py-1 text-sm shadow-sm transition-colors file:border-0 file:bg-muted file:text-sm file:font-medium file:text-foreground placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-50",
           className,
         )}
         ref={ref}

frontend/components/widgets/widget-card.tsx

@@ -37,9 +37,9 @@ export function WidgetCard({
   const typeIcon = widgetTypeIcons[widget.type] || <Activity className="h-3.5 w-3.5" />;
 
   return (
-    <Card className="group relative border-0 overflow-hidden rounded-2xl shadow-[0px_0px_0px_1px_var(--color-border)] hover:shadow-border-hover transition-all duration-200">
+    <Card className="group relative overflow-hidden rounded-2xl border border-border bg-card hover:shadow-border-hover transition-all duration-200">
       <div className={cn(
-        "absolute top-0 left-0 right-0 h-1 opacity-60 bg-ring"
+        "absolute top-0 left-0 right-0 h-0.5 opacity-40 bg-muted-foreground"
       )} />
       <CardHeader className="flex flex-row items-center justify-between pt-4 pb-2 px-4">
         <div className="flex items-center gap-2.5 min-w-0">
@@ -156,7 +156,7 @@ function ImageContent({ config }: { config: Record<string, unknown> }) {
     <img
       src={imageUrl}
       alt="Widget image"
-      className="max-h-48 w-full rounded-xl object-cover border border-border/20 shadow-sm"
+      className="max-h-48 w-full rounded-xl object-cover border border-border shadow-sm"
       onError={(e) => {
         (e.target as HTMLImageElement).style.display = "none";
       }}