Discord community: role sync, announcements webhook, launcher invite

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DjMbLQujBHunCCu5GpsHaT

panel/server/src/db.rs

@@ -668,6 +668,10 @@ const MIGRATIONS: &[&str] = &[
     CREATE TRIGGER guilds_rev_d AFTER DELETE ON guilds BEGIN UPDATE kv SET value = CAST(value AS INTEGER) + 1 WHERE key = 'guild_rev'; END;
     CREATE TRIGGER guilds_rev_u AFTER UPDATE OF name, tag, leader_uuid ON guilds BEGIN UPDATE kv SET value = CAST(value AS INTEGER) + 1 WHERE key = 'guild_rev'; END;
     "#,
+    // Discord role <-> panel group mapping.
+    r#"
+    ALTER TABLE groups ADD COLUMN discord_role TEXT NOT NULL DEFAULT '';
+    "#,
 ];
 
 pub async fn connect(data_dir: &Path) -> Result<SqlitePool> {