app-server: Add transport for remote control

codex-rs/state/migrations/0023_remote_control_enrollments.sql

@@ -0,0 +1,8 @@
+CREATE TABLE remote_control_enrollments (
+    websocket_url TEXT NOT NULL,
+    account_id TEXT NOT NULL,
+    server_id TEXT NOT NULL,
+    server_name TEXT NOT NULL,
+    updated_at INTEGER NOT NULL,
+    PRIMARY KEY (websocket_url, account_id)
+);