feat(telegram): per-chat command localization + unified locale resolver

Two related Telegram changes:

1. Per-chat command localization. setMyCommands now accepts a scope
   (BotCommandScopeChat) and deleteMyCommands clears scoped bindings.
   Command registration runs three tiers: default → per-language
   (Telegram client language) → per-chat (UI override). Saving a
   chat's language_override or commands_enabled toggle pushes the
   binding to Telegram inline rather than waiting on the 30s
   debounced bot-wide sync.

2. Unified Telegram locale resolution. Three test paths (bot test_chat,
   target receiver test, target-level fan-out) used to disagree on
   locale priority — the target receiver test in particular only
   consulted receiver.locale and ignored the chat's language_override.
   Introduced pick_telegram_locale (pure) and
   resolve_telegram_chat_locale (async DB lookup) in services/notifier
   so all three paths share one priority order:

       receiver.locale → chat.language_override → chat.language_code → fallback

   Fan-out keeps batch-loading TelegramChat rows for efficiency, just
   runs them through the same priority function now.

packages/core/src/notify_bridge_core/notifications/telegram/client.py

@@ -829,12 +829,41 @@ class TelegramClient:
 
     async def set_my_commands(
         self, commands: list[dict[str, str]], language_code: str | None = None,
+        scope: dict[str, Any] | None = None,
     ) -> dict[str, Any]:
-        """Register bot commands with BotFather API."""
+        """Register bot commands with BotFather API.
+
+        ``scope`` is a Telegram BotCommandScope object (e.g.
+        ``{"type": "chat", "chat_id": 123}``). When provided, the
+        registration applies only to that scope. ``language_code`` and
+        ``scope`` may be combined to localize per-scope.
+        """
         url = f"{TELEGRAM_API_BASE_URL}{self._token}/setMyCommands"
         payload: dict[str, Any] = {"commands": commands}
         if language_code:
             payload["language_code"] = language_code
+        if scope:
+            payload["scope"] = scope
+        try:
+            async with self._session.post(url, json=payload) as resp:
+                data = await resp.json()
+                if data.get("ok"):
+                    return {"success": True}
+                return {"success": False, "error": data.get("description", "Unknown error")}
+        except aiohttp.ClientError as err:
+            return {"success": False, "error": str(err)}
+
+    async def delete_my_commands(
+        self, language_code: str | None = None,
+        scope: dict[str, Any] | None = None,
+    ) -> dict[str, Any]:
+        """Clear bot commands for the given scope/language via BotFather API."""
+        url = f"{TELEGRAM_API_BASE_URL}{self._token}/deleteMyCommands"
+        payload: dict[str, Any] = {}
+        if language_code:
+            payload["language_code"] = language_code
+        if scope:
+            payload["scope"] = scope
         try:
             async with self._session.post(url, json=payload) as resp:
                 data = await resp.json()