feat(/add): add admin-only and link uniqueness handling

Wrap add_bounty call in try-except to handle PermissionError
and ValueError from admin check and link uniqueness check.

Fixes #45

apps/telegram-bot/commands.py

@@ -229,6 +229,7 @@ async def cmd_add(update: Update, ctx: ContextTypes.DEFAULT_TYPE) -> None:
     user_id = get_user_id(update)
     room_id = get_room_id(update)
 
+    try:
         bounty = BOUNTY_SERVICE.add_bounty(
             room_id=room_id,
             user_id=user_id,
@@ -236,6 +237,12 @@ async def cmd_add(update: Update, ctx: ContextTypes.DEFAULT_TYPE) -> None:
             link=link,
             due_date_ts=due_date_ts,
         )
+    except PermissionError as e:
+        await update.message.reply_text(f"⛔ {e}")
+        return
+    except ValueError as e:
+        await update.message.reply_text(f"⛔ {e}")
+        return
 
     due_str = ""
     if due_date_ts: