Feat: Add user roles for admin/owner powers

functions/api/schema.js

@@ -2,6 +2,7 @@ const schema = [
   `CREATE TABLE IF NOT EXISTS users (
     id INTEGER PRIMARY KEY,
     username TEXT UNIQUE NOT NULL,
+    role TEXT NOT NULL DEFAULT 'user' CHECK(role IN ('user', 'admin', 'owner')),
     created_at DATETIME DEFAULT CURRENT_TIMESTAMP
   );`,
   `CREATE TABLE IF NOT EXISTS subs (