fix: resolve React Error #310 and refactor admin section

- Fix React bug #33580: remove Suspense boundaries co-located with Link components
- Delete settings/loading.tsx and admin/loading.tsx (root cause of race condition)
- Convert all admin navigation from Next.js Link to anchor tags
- Move admin pages to dedicated (admin) route group
- Add AdminHeader matching main header visual design
- Add AdminSidebar with anchor-based navigation
- Add /api/admin/models route handler (replaces server actions for GET)
- Add /api/debug/client-error for server-side browser error reporting
- Add useNoteRefreshOptional() to fix crash in AdminHeader
- Hide Admin Dashboard menu for non-admin users
- Change app icons from yellow to blue (#3A7CA5) matching brand primary
- Fix admin search bar width to match main header

Made-with: Cursor

.claude/settings.local.json

@@ -0,0 +1,15 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(docker compose *)",
+      "mcp__web-search-prime__web_search_prime",
+      "WebSearch",
+      "mcp__zread__search_doc",
+      "mcp__zread__read_file",
+      "Bash(npm ls *)",
+      "mcp__zread__get_repo_structure",
+      "Bash(npm install *)",
+      "Bash(docker exec *)"
+    ]
+  }
+}