Cross-server network: shared economy groups for balances and guild banks

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

panel/server/src/db.rs

@@ -672,6 +672,10 @@ const MIGRATIONS: &[&str] = &[
     r#"
     ALTER TABLE groups ADD COLUMN discord_role TEXT NOT NULL DEFAULT '';
     "#,
+    // Servers can share one economy (balances and guild banks) by sharing a group name.
+    r#"
+    ALTER TABLE game_servers ADD COLUMN economy_group TEXT NOT NULL DEFAULT '';
+    "#,
 ];
 
 pub async fn connect(data_dir: &Path) -> Result<SqlitePool> {