feat: add Scheduler provider + multi-provider UX fixes

Scheduler provider:
- Virtual provider (no external service) that emits SCHEDULED_MESSAGE
  events on user-defined intervals or cron expressions
- Custom variables stored in tracker filters, flattened into template context
- fire_count persists across triggers via tracker state
- APScheduler CronTrigger support for cron-mode schedules
- Default templates (EN+RU), seeded on startup

Multi-provider UX fixes:
- Tracking config hides Immich-specific sections (periodic, scheduled,
  memory, asset display) for non-Immich providers
- Command config driven by provider capabilities — hides commands/settings
  for providers without bot commands
- Template config hides empty "Scheduled Messages" group
- Test menu on tracker targets is provider-aware (Immich shows all 4 test
  types, others show only basic)
- Removed redundant Test button from tracker card
- System-owned tracking configs (user_id=0) seeded for Gitea + Scheduler
- Fixed ownership checks to allow system configs in tracker-target links
- Capabilities cache shared across template-configs and command-configs
- Command tracker bot selector uses EntitySelect instead of raw select
- Sample context includes Gitea + Scheduler variables for template preview

packages/server/src/notify_bridge_server/services/sample_context.py

@@ -91,4 +91,50 @@ _SAMPLE_CONTEXT = {
     "photo_count": 30,
     "video_count": 5,
     "owner": "Alice",
+    # Gitea variables (for gitea provider templates)
+    "sender": "alexei",
+    "sender_name": "Alexei",
+    "sender_avatar": "",
+    "repo_name": "my-project",
+    "repo_full_name": "alexei/my-project",
+    "repo_url": "https://gitea.example.com/alexei/my-project",
+    "repo_description": "Example project",
+    "branch": "main",
+    "commits": [{"id": "abc1234567", "short_id": "abc1234", "message": "fix: example commit", "url": "", "author": "Alexei"}],
+    "commit_count": 1,
+    "compare_url": "https://gitea.example.com/alexei/my-project/compare/abc...def",
+    "issue_number": 42,
+    "issue_title": "Example issue",
+    "issue_url": "https://gitea.example.com/alexei/my-project/issues/42",
+    "issue_state": "open",
+    "issue_body": "",
+    "issue_labels": ["bug"],
+    "pr_number": 17,
+    "pr_title": "Add feature",
+    "pr_url": "https://gitea.example.com/alexei/my-project/pulls/17",
+    "pr_state": "open",
+    "pr_body": "",
+    "pr_merged": False,
+    "pr_base": "main",
+    "pr_head": "feature/example",
+    "pr_labels": [],
+    "comment_body": "Looks good!",
+    "comment_url": "",
+    "comment_author": "alexei",
+    "release_tag": "v1.0.0",
+    "release_name": "Version 1.0.0",
+    "release_url": "https://gitea.example.com/alexei/my-project/releases/tag/v1.0.0",
+    "release_body": "Initial release",
+    "release_draft": False,
+    "release_prerelease": False,
+    # Scheduler variables (for scheduler provider templates)
+    "schedule_name": "Daily Reminder",
+    "fire_count": 42,
+    "current_date": "22.03.2026",
+    "current_time": "09:00",
+    "current_datetime": "22.03.2026, 09:00 UTC",
+    "weekday": "Monday",
+    "custom_vars": {"team": "Engineering", "message": "Time for standup!"},
+    "team": "Engineering",
+    "message": "Time for standup!",
 }

packages/server/src/notify_bridge_server/services/scheduler.py

@@ -40,7 +40,7 @@ async def _load_tracker_jobs() -> None:
     from sqlmodel import select
     from sqlmodel.ext.asyncio.session import AsyncSession
     from ..database.engine import get_engine
-    from ..database.models import NotificationTracker
+    from ..database.models import NotificationTracker, ServiceProvider as ServiceProviderModel
 
     engine = get_engine()
     scheduler = get_scheduler()
@@ -49,11 +49,35 @@ async def _load_tracker_jobs() -> None:
         result = await session.exec(select(NotificationTracker).where(NotificationTracker.enabled == True))
         trackers = result.all()
 
+        # Pre-load provider types for scheduler detection
+        provider_types: dict[int, str] = {}
+        for tracker in trackers:
+            if tracker.provider_id not in provider_types:
+                provider = await session.get(ServiceProviderModel, tracker.provider_id)
+                if provider:
+                    provider_types[tracker.provider_id] = provider.type
+
     for tracker in trackers:
         job_id = f"tracker_{tracker.id}"
         if scheduler.get_job(job_id):
             continue
 
+        ptype = provider_types.get(tracker.provider_id, "")
+        filters = tracker.filters or {}
+
+        # Scheduler providers can use cron triggers
+        if ptype == "scheduler" and filters.get("schedule_type") == "cron":
+            cron_expr = filters.get("cron_expression", "")
+            if cron_expr:
+                try:
+                    _add_cron_job(scheduler, job_id, tracker.id, cron_expr, tracker.name)
+                    continue
+                except Exception as e:
+                    _LOGGER.error(
+                        "Invalid cron expression for tracker %d (%s): %s — falling back to interval",
+                        tracker.id, tracker.name, e,
+                    )
+
         scheduler.add_job(
             _poll_tracker,
             "interval",
@@ -65,23 +89,55 @@ async def _load_tracker_jobs() -> None:
         _LOGGER.info("Scheduled tracker %d (%s) every %ds", tracker.id, tracker.name, tracker.scan_interval)
 
 
-async def schedule_tracker(tracker_id: int, interval: int) -> None:
+def _add_cron_job(
+    scheduler: AsyncIOScheduler,
+    job_id: str,
+    tracker_id: int,
+    cron_expression: str,
+    tracker_name: str,
+) -> None:
+    """Add a cron-triggered job for a scheduler-type tracker."""
+    from apscheduler.triggers.cron import CronTrigger
+    trigger = CronTrigger.from_crontab(cron_expression)
+    scheduler.add_job(
+        _poll_tracker,
+        trigger,
+        id=job_id,
+        args=[tracker_id],
+        replace_existing=True,
+    )
+    _LOGGER.info("Scheduled tracker %d (%s) with cron: %s", tracker_id, tracker_name, cron_expression)
+
+
+async def schedule_tracker(
+    tracker_id: int,
+    interval: int,
+    cron_expression: str | None = None,
+) -> None:
     """Add or update a scheduler job for a tracker."""
     scheduler = get_scheduler()
     job_id = f"tracker_{tracker_id}"
+
+    # Remove existing job first to allow trigger type changes
     if scheduler.get_job(job_id):
-        scheduler.reschedule_job(job_id, trigger="interval", seconds=interval)
-        _LOGGER.info("Rescheduled tracker %d every %ds", tracker_id, interval)
-    else:
-        scheduler.add_job(
-            _poll_tracker,
-            "interval",
-            seconds=interval,
-            id=job_id,
-            args=[tracker_id],
-            replace_existing=True,
-        )
-        _LOGGER.info("Scheduled tracker %d every %ds", tracker_id, interval)
+        scheduler.remove_job(job_id)
+
+    if cron_expression:
+        try:
+            _add_cron_job(scheduler, job_id, tracker_id, cron_expression, f"tracker-{tracker_id}")
+            return
+        except Exception as e:
+            _LOGGER.error("Invalid cron for tracker %d: %s — using interval", tracker_id, e)
+
+    scheduler.add_job(
+        _poll_tracker,
+        "interval",
+        seconds=interval,
+        id=job_id,
+        args=[tracker_id],
+        replace_existing=True,
+    )
+    _LOGGER.info("Scheduled tracker %d every %ds", tracker_id, interval)
 
 
 async def unschedule_tracker(tracker_id: int) -> None:

packages/server/src/notify_bridge_server/services/watcher.py

@@ -94,6 +94,8 @@ def _event_allowed_by_config(event: ServiceEvent, tc: TrackingConfig) -> bool:
         "pr_merged": tc.track_pr_merged,
         "pr_commented": tc.track_pr_commented,
         "release_published": tc.track_release_published,
+        # Scheduler events
+        "scheduled_message": tc.track_scheduled_message,
     }
     return flag_map.get(event_type, True)
 
@@ -210,6 +212,8 @@ async def check_tracker(tracker_id: int) -> dict[str, Any]:
         provider_type = provider.type
         provider_config = dict(provider.config)
         provider_name = provider.name
+        tracker_name = tracker.name
+        tracker_filters = dict(tracker.filters) if tracker.filters else {}
         collection_ids = list(tracker.collection_ids or [])
 
     # Now create aiohttp session and poll
@@ -235,6 +239,15 @@ async def check_tracker(tracker_id: int) -> dict[str, Any]:
         # Gitea is webhook-based — events arrive via /api/webhooks/gitea endpoint.
         # The scheduler still calls check_tracker but there's nothing to poll.
         return {"status": "ok", "events_detected": 0, "collections_checked": 0}
+    elif provider_type == "scheduler":
+        from notify_bridge_core.providers.scheduler import SchedulerServiceProvider
+        custom_vars = tracker_filters.get("custom_variables", {})
+        sched = SchedulerServiceProvider(
+            name=provider_name,
+            tracker_name=tracker_name,
+            custom_variables=custom_vars,
+        )
+        events, new_state = await sched.poll(collection_ids, state_dict)
     else:
         return {"status": "error", "reason": f"unsupported provider type: {provider_type}"}