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

public/templates/standard/error/error.css

@@ -0,0 +1,18 @@
+.icon {
+    display: flex;
+    justify-content: center;
+    align-items: center;
+    font-size: 100pt;
+}
+
+.text {
+    text-align: center;
+    font-family: Verdana, Geneva, Tahoma, sans-serif;
+}
+
+.code {
+    font-family: monospace;
+    background-color: rgb(226, 225, 225);
+    padding: 1px;
+    border-radius: 5px;
+}