feat: chat language display, disabled EntitySelect items, dev scripts

Chat language:
- Added language_code field to TelegramChat model + migration
- Saved from message.from.language_code on webhook/polling
- Displayed as badge on bot chat cards and target receiver items
- Resolved from DB in target API response (works for existing receivers)
- Shown in chat picker dropdown (desc includes language)

EntitySelect improvements:
- Tracker-target link selector shows all targets, already-linked ones
  appear disabled with "Already linked" hint
- Receiver chat picker shows already-added chats as disabled

Dev scripts:
- scripts/restart-backend.sh and restart-frontend.sh
- Updated .claude/docs/dev-servers.md to reference scripts

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

@@ -7,7 +7,8 @@ from ..database.models import TelegramChat
 
 
 async def save_chat_from_webhook(
-    session: AsyncSession, bot_id: int, chat_data: dict
+    session: AsyncSession, bot_id: int, chat_data: dict,
+    language_code: str = "",
 ) -> None:
     """Save or update a chat entry from an incoming webhook message.
 
@@ -32,6 +33,8 @@ async def save_chat_from_webhook(
     if existing:
         existing.title = title
         existing.username = chat_data.get("username", existing.username)
+        if language_code:
+            existing.language_code = language_code
         session.add(existing)
     else:
         session.add(TelegramChat(
@@ -40,4 +43,5 @@ async def save_chat_from_webhook(
             title=title,
             chat_type=chat_data.get("type", "private"),
             username=chat_data.get("username", ""),
+            language_code=language_code,
         ))