Task #609: Per-user app enable/disable in Settings

- New `user_hidden_apps` table (userId+appId composite PK, cascade) in
  lib/db/src/schema/user-hidden-apps.ts; registered in schema index;
  pushed to dev DB via drizzle-kit.
- Backend (artifacts/api-server/src/routes/apps.ts):
  - GET /me/apps — returns every globally-active app visible to the
    user with a `hidden` flag.
  - PUT /me/apps/:appId/hidden — toggles a row in user_hidden_apps,
    gated by getVisibleAppsForUser + isActive so a user can't toggle
    apps they can't reach.
  - GET /apps (Home/Dock) now uses getVisibleNonHiddenAppsForUser so
    hidden apps disappear immediately.
- lib/appsVisibility.ts: added getHiddenAppIdsForUser and
  getVisibleNonHiddenAppsForUser helpers.
- OpenAPI: added /me/apps + /me/apps/{appId}/hidden, MyApp and
  UpdateMyAppHiddenBody schemas; regenerated api-zod + api-client-react.
- Frontend (settings-panel.tsx): added "My apps" accordion section as
  first GroupItem with MyAppsBody — Switch per app, optimistic update,
  invalidates getListMyAppsQueryKey + getListAppsQueryKey so Home/Dock
  refresh without reload.
- Translations: added settingsPanel.section.myApps + settingsPanel.myApps
  in ar.json + en.json.
- Code review fix: /me/apps and PUT gating filter isActive even for
  admins, so inactive apps don't appear in the Settings list.
- Proposed follow-up #611 (Playwright test that hidden apps disappear
  from Home and Dock).

artifacts/tx-os/src/locales/en.json

@@ -199,6 +199,7 @@
   "settingsPanel": {
     "title": "Settings",
     "section": {
+      "myApps": "My apps",
       "language": "Language",
       "notifications": "Notifications",
       "sound": "Sound",
@@ -210,6 +211,10 @@
     },
     "sound": {
       "master": "Play notification sounds"
+    },
+    "myApps": {
+      "loading": "Loading apps…",
+      "empty": "No apps available."
     }
   },
   "notifSettings": {