feat: Actions system — scheduled mutations on external services

Full-stack implementation of provider-scoped Actions with extensible
executor architecture. First action type: Immich auto_organize (sort
assets into albums by person, CLIP search, date range, favorites).

Core:
- ActionTypeDefinition registry + ActionExecutor ABC with execute/validate/dry-run
- ImmichActionExecutor with multi-album support and client-side filtering
- ImmichClient write methods: add/remove assets, create album, paginated search

Server:
- Action, ActionRule, ActionExecution DB models
- Full CRUD API + manual execute + dry-run + execution history endpoints
- APScheduler integration (interval + cron) for automated execution
- Action type discovery API + provider people endpoint

Frontend:
- Actions page with CRUD, execute/dry-run buttons, inline rule editor
- RuleEditor: person/album MultiEntitySelect pickers, criteria config
- ExecutionHistory: expandable per-rule result details
- MultiEntitySelect reusable component (searchable multi-pick palette)
- Notification tracker album picker migrated to MultiEntitySelect
- Fixed MdiIcon race condition (icons missing after cache-clearing reload)

packages/server/src/notify_bridge_server/main.py

@@ -35,6 +35,9 @@ from .api.app_settings import router as app_settings_router
 from .api.command_configs import router as command_configs_router
 from .api.command_trackers import router as command_trackers_router
 from .api.command_template_configs import router as command_template_configs_router
+from .api.actions import router as actions_router
+from .api.action_rules import router as action_rules_router
+from .api.action_types import router as action_types_router
 from .commands.webhook import router as webhook_router, set_webhook_secret
 from .api.webhooks import router as webhooks_router
 
@@ -106,6 +109,9 @@ app.include_router(matrix_bots_router)
 app.include_router(users_router)
 app.include_router(status_router)
 app.include_router(app_settings_router)
+app.include_router(action_types_router)
+app.include_router(action_rules_router)
+app.include_router(actions_router)
 app.include_router(command_configs_router)
 app.include_router(command_trackers_router)
 app.include_router(command_template_configs_router)