fix(cache): prevent caching of admin files and API responses

CRITICAL FIX: Automatic cache invalidation for admin JavaScript files.

Root cause: Service worker and browser cache serving stale admin files
even after deploying fixes. Users had to manually clear cache daily.

Changes:
1. Service Worker (v0.1.2):
   - Added NEVER_CACHE_PATHS for /js/admin/, /api/, /admin/
   - These paths now ALWAYS fetch from network, never cache
   - Bumped version to trigger cache clear on all clients

2. Server-side Cache Control:
   - Added Cache-Control: no-store headers for admin/API paths
   - Added Pragma: no-cache and Expires: 0 for belt-and-suspenders
   - Prevents browser AND proxy caching

This ensures:
- Admin JavaScript updates deploy immediately
- API responses are never stale
- No more manual cache clearing required

Testing:
- Admin files will now always be fresh from server
- Service worker will auto-update to v0.1.2 on next visit
- Browsers will respect no-cache headers going forward

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

public/service-worker.js

@@ -5,10 +5,17 @@
  * - PWA functionality
  */
 
-const CACHE_VERSION = '0.1.1';
+const CACHE_VERSION = '0.1.2';
 const CACHE_NAME = `tractatus-v${CACHE_VERSION}`;
 const VERSION_CHECK_INTERVAL = 3600000; // 1 hour in milliseconds
 
+// Paths that should NEVER be cached (always fetch fresh from network)
+const NEVER_CACHE_PATHS = [
+  '/js/admin/',           // Admin JavaScript - always fresh
+  '/api/',                // API calls
+  '/admin/'               // Admin pages
+];
+
 // Assets to cache immediately on install
 const CRITICAL_ASSETS = [
   '/',
@@ -61,6 +68,16 @@ self.addEventListener('fetch', (event) => {
     return;
   }
 
+  // NEVER CACHE: Admin files, API calls - always fetch fresh, never cache
+  if (NEVER_CACHE_PATHS.some(path => url.pathname.startsWith(path))) {
+    event.respondWith(
+      fetch(request).catch(() => {
+        throw new Error('Network required for admin/API resources');
+      })
+    );
+    return;
+  }
+
   // HTML files: Network-ONLY (never cache, always fetch fresh)
   // This ensures users always get the latest content without cache refresh
   if (request.destination === 'document' || url.pathname.endsWith('.html')) {

src/middleware/security-headers.middleware.js

@@ -56,6 +56,15 @@ function securityHeadersMiddleware(req, res, next) {
     'geolocation=(), microphone=(), camera=(), payment=()'
   );
 
+  // Cache Control: NEVER cache admin files or API responses
+  if (req.path.startsWith('/admin/') ||
+      req.path.startsWith('/js/admin/') ||
+      req.path.startsWith('/api/')) {
+    res.setHeader('Cache-Control', 'no-store, no-cache, must-revalidate, proxy-revalidate');
+    res.setHeader('Pragma', 'no-cache');
+    res.setHeader('Expires', '0');
+  }
+
   next();
 }