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

@@ -105,8 +105,6 @@ def format_bounty(b, show_id: bool = True, slice_length: int = 0) -> str:
             parts.append(f"⏰ Today (OVERDUE)")
         else:
             parts.append(f"⏰ {due_str} ({days_left}d)")
-    if b.created_by_user_id:
-        parts.append(f"by {b.created_by_user_id}")
     return " | ".join(parts)
 
 
@@ -231,6 +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,
@@ -238,6 +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: