fix: use absolute db path in production for Docker

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/db/index.ts

@@ -8,7 +8,11 @@ let _db: Database.Database | null = null
 export function getDb(): Database.Database {
   if (_db) return _db
 
-  const dbPath = process.env.DB_PATH || resolve(process.cwd(), 'data', 'rebalancer.db')
+  const dbPath =
+    process.env.DB_PATH ||
+    (process.env.NODE_ENV === 'production'
+      ? '/app/data/rebalancer.db'
+      : resolve(process.cwd(), 'data', 'rebalancer.db'))
   mkdirSync(dirname(dbPath), { recursive: true })
 
   _db = new Database(dbPath)