feat: Add bantime and goroutines for unban expires ban

internal/storage/migrations.go

@@ -17,7 +17,8 @@ CREATE TABLE IF NOT EXISTS bans (
 	id INTEGER PRIMARY KEY,
 	ip TEXT UNIQUE NOT NULL,
 	reason TEXT,
-	banned_at DATETIME DEFAULT CURRENT_TIMESTAMP
+	banned_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+	expired_at DATETIME
 );
 
 CREATE INDEX IF NOT EXISTS idx_service ON requests(service);