feat: public platform, admin console, templates, landing docs

Projects become publicly browsable after admin approval; management and
secret-adjacent reads (logs, variables, exec, connection URLs) require
owner/member/admin auth, and platform controls sit behind RequireAdmin.

- Backend: OptionalAuth middleware, read/authed/admin route groups,
  projects.is_approved + service_templates.owner_id migration,
  visibility-aware sqlc queries, admin overview/users/approval endpoints,
  EnsureAdminAccount bootstrap (ADMIN_* env), 30 seeded templates with
  owner CRUD, managed-database connection URLs gated owner+admin, fix
  DB.Stats() infinite recursion.
- Frontend: expandable persisted sidebar + clickable user menu, public
  landing page with searchable docs browser (GitHub sync, bundled
  snapshot + localStorage fallback), DocsBrowser shared with /docs,
  template create/edit/JSON-upload for owned templates, database create
  dialog, admin console (stats, approvals, project edit/delete, user
  admin toggles), HA/Security/Usage polish with dead CSS tokens mapped
  to real theme vars, anonymous-safe gating on every mutation control.
- Tests: safe window.localStorage access fixes happy-dom crashes in
  PlatformShell and canvas storage.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/api/exec.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
 
 	"containr/internal/database"
 	"containr/internal/docker"
@@ -17,7 +18,6 @@ import (
 // commands run as the container's default user with a 30s ceiling.
 func handleExecInService(c *gin.Context) {
 	serviceID := c.Param("id")
-	userID := c.MustGet("user_id").(string)
 	db := c.MustGet("db").(*database.DB)
 
 	var req struct {
@@ -33,17 +33,20 @@ func handleExecInService(c *gin.Context) {
 		return
 	}
 
-	var ownerID string
-	err := db.QueryRow(
-		`SELECT p.owner_id FROM services s
-		 JOIN projects p ON p.id = s.project_id
-		 WHERE s.id = $1`,
-		serviceID,
-	).Scan(&ownerID)
-	if err != nil || ownerID != userID {
+	serviceUUID, err := uuid.Parse(serviceID)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid service ID"})
+		return
+	}
+	projectID, found := serviceProjectID(db, serviceUUID)
+	if !found {
 		c.JSON(http.StatusNotFound, gin.H{"error": "Service not found"})
 		return
 	}
+	if _, allowed := projectManageAccess(c, db, projectID); !allowed {
+		c.JSON(http.StatusForbidden, gin.H{"error": "Access denied"})
+		return
+	}
 
 	dockerClient, _ := c.Get("docker_client")
 	dockerCli, _ := dockerClient.(*docker.Client)