feat: comprehensive code review fixes + receivers-only architecture

Security:
- Refuse startup with default secret_key in production (was just logging)
- Settings endpoint now requires admin role
- Password validation on initial setup
- DOM-based HTML sanitizer replaces regex in template previews
- Add *.log to .gitignore

Performance & reliability:
- Token refresh deduplication prevents race condition on concurrent 401s
- Theme media query listener registered once (no leak)
- IconPicker uses $derived instead of function call per render
- Snackbar uses single-batch state update instead of while loop
- Replace 11 inline hover handlers with CSS :hover in layout

Architecture - receivers-only:
- Delivery endpoints (chat_id, email, url, room_id, topic) now stored
  exclusively in TargetReceiver rows, never in target.config
- Migration extracts existing delivery fields to receiver rows
- Notifier and dispatcher remove all config fallbacks
- Frontend targets page shows receivers list per target with
  add/remove/toggle/test per receiver
- Single-receiver test endpoint: POST /targets/{id}/receivers/{id}/test

Code quality:
- Extract AuthLayout.svelte from login/setup (150 lines CSS dedup)
- Split telegram-bots page (754→51 lines + 3 tab components)
- Split notification-trackers page (547→432 lines + 4 components)
- Deduplicate _send_reply into shared handler.send_reply()
- Add locale column to template models, replace name-based detection
- Fix delete_notification_tracker dead protection check
- Fix check_telegram_bot query (filter by type, remove bogus OR)
- Add graceful scheduler shutdown in lifespan
- Consistent /bots?tab=telegram URLs across all nav links

i18n:
- Error page, chat actions, target types, provider types internationalized
- All new receiver UI strings in EN + RU

packages/server/src/notify_bridge_server/main.py

@@ -39,13 +39,15 @@ async def lifespan(app: FastAPI):
     await init_db()
     # Run data migrations (idempotent)
     from .database.engine import get_engine
-    from .database.migrations import migrate_schema, migrate_tracker_targets, migrate_entity_refactor, migrate_template_slots, migrate_target_receivers
+    from .database.migrations import migrate_schema, migrate_tracker_targets, migrate_entity_refactor, migrate_template_slots, migrate_target_receivers, migrate_template_locale, migrate_receivers_from_config
     engine = get_engine()
     await migrate_schema(engine)
     await migrate_tracker_targets(engine)
     await migrate_entity_refactor(engine)
     await migrate_template_slots(engine)
     await migrate_target_receivers(engine)
+    await migrate_template_locale(engine)
+    await migrate_receivers_from_config(engine)
     await _seed_default_templates()
     await _seed_default_command_templates()
     # Configure webhook secret from DB setting (falls back to env var)
@@ -54,9 +56,13 @@ async def lifespan(app: FastAPI):
     async with _AS(engine) as _session:
         _secret = await _get_setting(_session, "telegram_webhook_secret")
     set_webhook_secret(_secret or None)
-    from .services.scheduler import start_scheduler
+    from .services.scheduler import start_scheduler, get_scheduler
     await start_scheduler()
     yield
+    # Graceful shutdown
+    scheduler = get_scheduler()
+    if scheduler.running:
+        scheduler.shutdown()
 
 
 app = FastAPI(title="Notify Bridge", version="0.1.0", lifespan=lifespan)
@@ -108,7 +114,8 @@ async def _seed_default_templates():
         )
         system_configs = result.all()
         existing_locales = {
-            "ru" if "(RU)" in c.name else "en": c for c in system_configs
+            (c.locale if c.locale else ("ru" if "(RU)" in c.name else "en")): c
+            for c in system_configs
         }
 
         for locale in ("en", "ru"):
@@ -144,6 +151,8 @@ async def _seed_default_templates():
                         values[col] = "%d.%m.%Y, %H:%M UTC"
                     elif col == "date_only_format":
                         values[col] = "%d.%m.%Y"
+                    elif col == "locale":
+                        values[col] = locale
                     else:
                         values[col] = ""  # empty string for legacy columns
                 cols_str = ", ".join(values.keys())
@@ -211,6 +220,7 @@ async def _seed_default_command_templates():
                     provider_type="immich",
                     name=name,
                     description=f"Default Immich command templates ({locale.upper()})",
+                    locale=locale,
                 )
                 session.add(config)
                 await session.flush()
@@ -227,7 +237,7 @@ async def _seed_default_command_templates():
             )
             system_configs = result.all()
             for config in system_configs:
-                locale = "ru" if "(RU)" in config.name else "en"
+                locale = config.locale if config.locale else ("ru" if "(RU)" in config.name else "en")
                 slots = load_default_command_templates(locale)
                 if not slots:
                     continue