feat(mobile): env editing, domains, scaling, notifications (#61)

Companion app was read-mostly — quick fixes still needed a workstation.

- service/variables: full env editor — add/edit/delete rows, secret
  toggle, masked-secret preservation (untouched secrets resubmit the
  "********" placeholder so stored ciphertext survives the PUT).
- service/domains: list with default/TLS status, add, remove,
  set-default.
- service/settings: replicas stepper (0–16), container port, scale-to-
  zero toggle + idle minutes — saves via PUT /services/:id.
- (tabs)/notifications: alerts tab with unread badge on the tab bar,
  mark-read per item and mark-all.
- Service detail gains a Manage section linking all three screens.

State initializes at mount inside a child component rather than an
effect — post-save refetches no longer clobber in-flight edits, and
the react-hooks/set-state-in-effect lint stays clean.

Verified: tsc --noEmit, expo lint, expo export (android bundle,
1378 modules — router graph compiles).

Authored By: TDvorak <[email protected]>

app/mobile/src/app/(tabs)/_layout.tsx

@@ -1,9 +1,19 @@
 import React from 'react';
 import { Tabs } from 'expo-router';
 import { Ionicons } from '@expo/vector-icons';
+import { useQuery } from '@tanstack/react-query';
+import { useApi } from '../../session';
 import { colors } from '../../theme';
 
 export default function TabsLayout() {
+  const api = useApi();
+  const notifs = useQuery({
+    queryKey: ['notifications'],
+    queryFn: () => api.notifications(),
+    refetchInterval: 60_000,
+  });
+  const unread = notifs.data?.unread ?? 0;
+
   return (
     <Tabs
       screenOptions={{
@@ -41,6 +51,16 @@ export default function TabsLayout() {
           ),
         }}
       />
+      <Tabs.Screen
+        name="notifications"
+        options={{
+          title: 'Alerts',
+          tabBarBadge: unread > 0 ? unread : undefined,
+          tabBarIcon: ({ color, size }) => (
+            <Ionicons name="notifications-outline" size={size} color={color} />
+          ),
+        }}
+      />
       <Tabs.Screen
         name="settings"
         options={{