refactor: refactor for modern layout

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

backend/coconut-leaf.template.toml

@@ -0,0 +1,22 @@
+[database]
+driver = "sqlite"
+
+[database.config]
+path = "coconut-leaf.db"
+
+# [database]
+# driver = "mysql"
+# 
+# [database.config]
+# host = "localhost"
+# port = 3306
+# user = "root"
+# password = "password"
+# database = "coconut_leaf"
+
+[web]
+port = 8888
+
+[others]
+auto-token-clean-duration = 86400
+debug = true