fix(moderation): resolve @username via Telegram API fallback in _resolve_user_id

Add bot.get_chat() as a third fallback when resolving @username targets,
after admin list and known_users lookups. Fixes /unban (and /ban, /mute,
/unmute) failing for users not yet tracked in known_users.

Also update UNBAN_USAGE string to mention @username as a valid option.

Author: 0xMett

src/python_italy_bot/handlers/moderation.py

@@ -623,6 +623,13 @@ async def _resolve_user_id(
             known = await moderation_service.get_known_user_by_username(username_lower)
             if known is not None:
                 return known.user_id
+        # Try Telegram API as last resort
+        try:
+            resolved_chat = await context.bot.get_chat(f"@{username_lower}")
+            if resolved_chat.id:
+                return resolved_chat.id
+        except Exception:
+            pass
         return None
     if re.match(r"^-?\d+$", target):
         return int(target)

src/python_italy_bot/strings.py

@@ -101,7 +101,7 @@ def ban_notification(
 
 
 # Unban
-UNBAN_USAGE = "Uso: /unban user_id, o rispondi al messaggio con /unban"
+UNBAN_USAGE = "Uso: /unban user_id|@username, o rispondi al messaggio con /unban"
 
 
 def unban_success(success_count: int, fail_count: int) -> str: