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/commands/handler.py

@@ -541,6 +541,25 @@ def _format_assets(
     })
 
 
+async def send_reply(bot_token: str, chat_id: str, text: str) -> None:
+    """Send a text reply via Telegram Bot API, retrying without HTML on parse failure."""
+    async with aiohttp.ClientSession() as http:
+        url = f"{TELEGRAM_API_BASE_URL}{bot_token}/sendMessage"
+        payload: dict[str, Any] = {"chat_id": chat_id, "text": text, "parse_mode": "HTML"}
+        try:
+            async with http.post(url, json=payload) as resp:
+                if resp.status != 200:
+                    result = await resp.json()
+                    _LOGGER.debug("Telegram reply failed: %s", result.get("description"))
+                    if "parse" in str(result.get("description", "")).lower():
+                        payload.pop("parse_mode", None)
+                        async with http.post(url, json=payload) as retry_resp:
+                            if retry_resp.status != 200:
+                                _LOGGER.warning("Telegram reply failed on retry")
+        except aiohttp.ClientError as err:
+            _LOGGER.error("Failed to send Telegram reply: %s", err)
+
+
 async def send_media_group(
     bot_token: str, chat_id: str, media_items: list[dict[str, Any]],
 ) -> None: