feat: deferred dispatch, release-check provider, settings polish

- Defer quiet-hours dispatches into new deferred_dispatch table; drain
  job + periodic catch-up scan re-fire at window end with coalescing on
  (link, event_type, collection_id).
- Add ON DELETE SET NULL migration on event_log_id and partial unique
  index on (link_id, collection_id, event_type) WHERE status='pending'.
- Add release-check provider abstraction (Gitea/GitHub) with SSRF-safe
  URL validation, settings UI cassette, and scheduled polling.
- Replace importlib-only version lookup with version.py helper that
  prefers the higher of installed metadata vs source pyproject so stale
  editable dev installs stop misreporting.
- Aurora frontend polish: MetaStrip component, ReleaseCassette,
  EventDetailModal expansion, and i18n additions.

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

@@ -42,8 +42,9 @@ from ..database.models import (
     TrackingConfig,
 )
 from .dispatch_helpers import (
+    GateReason,
     apply_tracking_display_filters,
-    event_allowed_by_config,
+    evaluate_event_gate,
     get_app_timezone,
     load_link_data,
 )
@@ -262,7 +263,11 @@ async def dispatch_scheduled_for_tracker(
                 if tc is not None:
                     if not getattr(tc, f"{kind}_enabled", True):
                         continue
-                    if not event_allowed_by_config(event, tc, app_tz):
+                    # Scheduled / periodic / memory dispatches are wall-clock
+                    # by nature — a "good morning" delivered at 3 pm is wrong,
+                    # so quiet hours = drop (not defer) for these kinds. The
+                    # other gate (per-event-type flag) still applies.
+                    if not evaluate_event_gate(event, tc, app_tz).allowed:
                         continue
                 if tmpl is None:
                     continue