Add customizable home dashboard with per-user pinned apps

- Users can pin/unpin any available service on their home page via a
  Customize mode; preferences persisted via PATCH /api/users/me/preferences
- Time-aware greeting renders the user's display name through React JSX
  (HTML-escaped by design — no dangerouslySetInnerHTML used)
- Added dashboard_app_ids JSON column to users table (migration c7e8f9a0b1d2)
- /settings now routes to a placeholder page

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/api/client.ts

@@ -30,6 +30,16 @@ export interface UserData {
 
 export const getMe = () => api.get<UserData>("/users/me").then((r) => r.data);
 
+export interface DashboardPrefs {
+  app_ids: string[];
+}
+
+export const getDashboardPrefs = () =>
+  api.get<DashboardPrefs>("/users/me/preferences").then((r) => r.data);
+
+export const updateDashboardPrefs = (app_ids: string[]) =>
+  api.patch<DashboardPrefs>("/users/me/preferences", { app_ids }).then((r) => r.data);
+
 // --- Admin ---
 export interface AdminUserCreate {
   email: string;