refactor: refactor for modern layout

- split frontend and backend.
- update backend with modern Python dev strategies.

.gitignore

@@ -1,16 +1,3 @@
-# ignore sqlite db
-*.db
-
-# ignore my debug setting
-*.cfg
-
-# ignore py cache
-src/__pycache__
-
-# ignore any image first
-*.png
-*.jpg
-*.gif
-
-# elimate vscode
-.vscode
+## ======== Personal ========
+# Ignore VSCode
+.vscode/