fix(web): skip empty Authorization header for forward-auth proxy compatibility

Centralize duplicated getToken() + Bearer header logic into a single
formatHeaders() helper in lib/api.ts. When no token exists, the
Authorization header is omitted entirely instead of sending an empty
Bearer token, which breaks forward-auth proxies like Authelia behind
Caddy.

Changes:
- Add formatHeaders() with try-catch around localStorage access
- Replace 20+ duplicated getToken() definitions across tool components
- Migrate all call sites including file-details, settings, change-password
- Update tests to verify header omission on empty token

Based on the fix proposed by @jules2689 in #6, with improvements:
file placement (lib/api.ts vs components), localStorage error handling,
simplified truthiness check, and complete call-site coverage.

Co-Authored-By: Julian Nadeau <julian@jnadeau.ca>

apps/web/src/pages/change-password-page.tsx

@@ -1,4 +1,5 @@
 import { type FormEvent, useRef, useState } from "react";
+import { formatHeaders } from "@/lib/api";
 
 /**
  * Trigger the browser's "Save Password" prompt by submitting a real form
@@ -85,13 +86,9 @@ export function ChangePasswordPage() {
 
     setLoading(true);
     try {
-      const token = localStorage.getItem("stirling-token");
       const res = await fetch("/api/auth/change-password", {
         method: "POST",
-        headers: {
-          "Content-Type": "application/json",
-          Authorization: `Bearer ${token}`,
-        },
+        headers: formatHeaders({ "Content-Type": "application/json" }),
         body: JSON.stringify({ currentPassword, newPassword }),
       });