fix: comprehensive API/UI review — 26 bug fixes and improvements

Backend:
- Scheduler lifecycle sync: create/update/delete tracker now syncs APScheduler jobs
- Test-periodic/test-memory endpoints render actual Jinja2 templates with sample data
- Cascade cleanup on tracker delete (TrackerState removed, EventLog nullified)
- Fix user_id=0 FK violation for system-owned TemplateConfig (removed FK constraint)
- Fix API key leak: only attach x-api-key header for internal provider URLs
- Validate config ownership in tracker_targets create/update
- Fix _response() double-emit of created_at in template/tracking configs
- Add per-target-link test endpoints (test, test-periodic, test-memory)

Frontend:
- Fix orphaned provider on test exception in providers/new
- Add submitting guard + disabled state to targets save button
- Move test buttons from tracker card to per-target-link rows
- Fix Svelte 5 async $state reactivity (spread reassignment for all Record mutations)
- i18n for dashboard timeAgo and event type badges (EN + RU)
- Add required attribute to chat select dropdown in targets
- Fix font CSS vars to prioritize imported DM Sans / JetBrains Mono
- Standardize empty states with centered icon + text across all 6 list pages
- Add stagger-children animation class to all list containers
- Fix slide transition duration consistency (200ms everywhere)
- Standardize border-radius to rounded-md across all form inputs
- Fix providers/new page structure (h2 + mb-8 spacing)
- Fix tracker card action row overflow (flex-wrap justify-end)
- JinjaEditor dark mode reactivity (recreate editor on theme change)
- Add aria-labels to mobile nav items
- Make ConfirmModal confirm button label/icon configurable
- Remove double error reporting on providers page
- Add telegram bot edit functionality (name editing via PUT)
- i18n for External Domain label on provider forms

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -57,6 +57,34 @@ 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:
+    """Add or update a scheduler job for a tracker."""
+    scheduler = get_scheduler()
+    job_id = f"tracker_{tracker_id}"
+    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)
+
+
+async def unschedule_tracker(tracker_id: int) -> None:
+    """Remove a scheduler job for a tracker."""
+    scheduler = get_scheduler()
+    job_id = f"tracker_{tracker_id}"
+    if scheduler.get_job(job_id):
+        scheduler.remove_job(job_id)
+        _LOGGER.info("Unscheduled tracker %d", tracker_id)
+
+
 async def _poll_tracker(tracker_id: int) -> None:
     """Poll a tracker for changes."""
     from .watcher import check_tracker