feat: register bot commands with Telegram

Call setMyCommands at startup so clients show the command list in the
/ menu. handlers::register_commands wraps Command::bot_commands()
(teloxide derives it from the #[command(description)] attributes);
a registration failure only warns and does not stop the bot.

crates/xmedia-bot/src/main.rs

@@ -44,6 +44,11 @@ async fn main() {
 
     let bot = Bot::from_env();
 
+    // Register the command list with Telegram (client `/` menu).
+    if let Err(e) = handlers::register_commands(&bot).await {
+        log::warn!("failed to register commands: {e}");
+    }
+
     log::info!(
         "config: {} admin(s), edit-message TTL {}s",
         CONFIG.admin_ids.len(),