feat: store username when creating bounty for display

When adding a bounty, capture effective_user's username or first_name
and store it for display in /show. Now shows actual name instead of
just "User".

apps/telegram-bot/commands.py

@@ -359,6 +359,9 @@ async def cmd_add(update: Update, ctx: ContextTypes.DEFAULT_TYPE) -> None:
     room_id = get_room_id(update)
     timezone_str = BOUNTY_SERVICE.get_timezone(room_id)
 
+    effective_user = update.effective_user
+    username = effective_user.username or effective_user.first_name or None
+
     text, link, due_date_ts, _, _ = parse_args(args, timezone_str)
     if not text and not link:
         await update.message.reply_text("A bounty needs at least text or a link.")
@@ -371,6 +374,7 @@ async def cmd_add(update: Update, ctx: ContextTypes.DEFAULT_TYPE) -> None:
             text=text,
             link=link,
             due_date_ts=due_date_ts,
+            created_by_username=username,
         )
     except PermissionError as e:
         await update.message.reply_text(f"⛔ {e}")
@@ -662,7 +666,10 @@ async def cmd_show(update: Update, ctx: ContextTypes.DEFAULT_TYPE) -> None:
         due_str = dt_due.strftime("%d %B %Y %H:%M")
         lines.append(f"📅 {due_str} ({timezone_str})")
 
-    lines.append(f'👤 <a href="tg://user?id={bounty.created_by_user_id}">User</a>')
+    display_name = bounty.created_by_username or f"User {bounty.created_by_user_id}"
+    lines.append(
+        f'👤 <a href="tg://user?id={bounty.created_by_user_id}">{display_name}</a>'
+    )
 
     dt_created = datetime.fromtimestamp(bounty.created_at, tz=tz)
     created_str = dt_created.strftime("%Y-%m-%d %H:%M")