Refactor API structure: add internal handling, update templates, and remove deprecated files

public/templates/templates.json

@@ -1,28 +1,6 @@
 {
-    "error":{
-        "name":"error",
-        "dir_name":"error",
-        "html_file":"error.html",
-        "css_files":[
-            "error.css"
-        ]
-    },
-    "setup":{
-        "name":"setup",
-        "dir_name":"setup",
-        "html_file":"setup.html",
-        "css_files":[]
-    },
-    "entrys_frontend":{
-        "name":"entrys_frontend",
-        "dir_name":"entrys_frontend",
-        "html_file":"entrys_frontend.html",
-        "css_files":[]
-    },
-    "login":{
-        "name":"login",
-        "dir_name":"login",
-        "html_file":"login.html",
-        "css_files":[]
+    "standard":{
+        "name":"Standard Template",
+        "dir_name":"standard"
     }
 }