implemented 0.db as admin database architecture + updated test file

tests/debug_hset.rs

@@ -28,6 +28,7 @@ async fn debug_hset_simple() {
         encrypt: false,
         encryption_key: None,
         backend: herodb::options::BackendType::Redb,
+        admin_secret: "test-admin".to_string(),
     };
     
     let mut server = Server::new(option).await;
@@ -48,6 +49,12 @@ async fn debug_hset_simple() {
     sleep(Duration::from_millis(200)).await;
     
     let mut stream = TcpStream::connect(format!("127.0.0.1:{}", port)).await.unwrap();
+    // Acquire ReadWrite permissions on this connection
+    let resp = send_command(
+        &mut stream,
+        "*4\r\n$6\r\nSELECT\r\n$1\r\n0\r\n$3\r\nKEY\r\n$10\r\ntest-admin\r\n",
+    ).await;
+    assert!(resp.contains("OK"), "Failed SELECT handshake: {}", resp);
     
     // Test simple HSET
     println!("Testing HSET...");