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/handlers.rs

@@ -393,6 +393,15 @@ fn plural(n: usize) -> &'static str {
     if n == 1 { "y" } else { "ies" }
 }
 
+/// Registers the bot's command list with Telegram so clients show it in the
+/// `/` menu (Bot API `setMyCommands`).
+pub async fn register_commands(bot: &Bot) -> Result<(), RequestError> {
+    let commands = Command::bot_commands();
+    bot.set_my_commands(commands.clone()).await?;
+    log::info!("registered {} commands", commands.len());
+    Ok(())
+}
+
 /// For locally produced media (encoded ugoira MP4) the thumbnail URL is a
 /// hotlink-protected remote URL Telegram may not fetch; let Telegram generate
 /// its own thumbnail instead.

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(),