feat(ui): Create content pattern components - DataTable, FilterBar, EmptyState, LoadingState

- Add LoadingState with table, card, list, and text skeleton patterns
- Add EmptyState with customizable icon, title, description, and action slot
- Add FilterBar with search input, clear button, and custom filter slot
- Add DataTable with TanStack Table integration, sorting, and row click
- Create barrel export index.ts for common components
- Install tanstack-table-8-svelte-5 for Svelte 5 compatibility
- Sync auth spec with authenticated user redirect requirements
- Archive p03-dashboard-enhancement

Refs: openspec/changes/p04-content-patterns
Closes: p04-content-patterns

frontend/package.json

@@ -49,6 +49,7 @@
     "lucide-svelte": "^0.574.0",
     "recharts": "^2.15.1",
     "sveltekit-superforms": "^2.24.0",
+    "tanstack-table-8-svelte-5": "^0.1.2",
     "zod": "^3.24.2"
   }
 }