Refactor app by modularizing components and extracting utilities.

The changes split large features into smaller, reusable components like `AdminPanel`, `LoginPage`, `TopBar`, `PasswordModal`, and `ChipModal`. Utility functions such as `cycleTag` and `chipStorage` were extracted for better organization. This improves the code's readability, maintainability, and scalability.

frontend/src/api/client.js

@@ -0,0 +1,11 @@
+import { API_BASE } from "../constants";
+
+export async function api(path, opts = {}) {
+  const res = await fetch(API_BASE + path, {
+    credentials: "include",
+    headers: { "Content-Type": "application/json" },
+    ...opts,
+  });
+  if (!res.ok) throw new Error(await res.text());
+  return res.json();
+}