chore: move notifications backend to proper DI

The send() dispatcher (services/notificationService.ts) and the in-app store
(services/inAppNotifications.ts) fold together into the DI-native
NotificationsService over DatabaseService + RealtimeService; the prefs
matrix, transports, channel registry and inAppNotificationActions stay plain
infra modules. A 1-export notifications.bridge covers scheduler, legacy
adminService/memories and the six lazy fire-and-forget sends; AdminController
and the plugin RPC host (24th factory dep) inject. The 5-tool registrar +
notifications-in-app resource move to notifications.mcp.ts. Tests move with
case IDs preserved (NSVC-*, INOTIF-*, + NSVC-020 bridge pin); ~18 suites
repoint path mocks/warm-ups; the module e2e goes DI-native.

Also carries the verified-quirk fixes that would normally trail as a
separate fix(server) commit (file-overlap with the fold): toUtcIso on all
three created_at paths (INOTIF-013/014), respond claims the response CAS
before running the action handler with release-on-failure (INOTIF-011/012),
synology's fire-and-forget send gains .catch, the dispatch-failure log
unwraps Error messages (NSVC-021), and the MCP resource description drops
its false 'unread first' claim.

server/tests/helpers/mcp-test-controllers.ts

@@ -22,6 +22,8 @@ import { DaysMcp } from '../../src/nest/days/days.mcp';
 import { DaysService } from '../../src/nest/days/days.service';
 import { MapsMcp } from '../../src/nest/maps/maps.mcp';
 import { MapsService } from '../../src/nest/maps/maps.service';
+import { NotificationsMcp } from '../../src/nest/notifications/notifications.mcp';
+import { NotificationsService } from '../../src/nest/notifications/notifications.service';
 import { PackingMcp } from '../../src/nest/packing/packing.mcp';
 import { PackingService } from '../../src/nest/packing/packing.service';
 import { PermissionsService } from '../../src/nest/permissions/permissions.service';
@@ -100,6 +102,7 @@ export function createMcpTestRegistry(): McpRegistry {
       new CollectionsMcp(new CollectionsService(dbService, permissionsService, realtimeService), dbService, authService),
       new TransitMcp(new TransitService(), daysService, reservationsService, dbService, authService),
       new AtlasMcp(new AtlasService(dbService)),
+      new NotificationsMcp(new NotificationsService(dbService, realtimeService), authService),
     ],
     { accessPolicy: trekMcpAccessPolicy, validateAccess: trekMcpValidateAccess },
   );