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

@@ -229,13 +229,20 @@ async def cmd_add(update: Update, ctx: ContextTypes.DEFAULT_TYPE) -> None:
     user_id = get_user_id(update)
     room_id = get_room_id(update)
 
-    bounty = BOUNTY_SERVICE.add_bounty(
-        room_id=room_id,
-        user_id=user_id,
-        text=text,
-        link=link,
-        due_date_ts=due_date_ts,
-    )
+    try:
+        bounty = BOUNTY_SERVICE.add_bounty(
+            room_id=room_id,
+            user_id=user_id,
+            text=text,
+            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: