feat: Add PWA support and consolidate CSS design system

- Add PWA manifest, icons (192x192, 512x512), and service worker
- Register service worker in index.html with Apple mobile web app support
- Consolidate CSS variables and design tokens documentation
- Update PrimeVue overrides for consistent theming
- Refactor data-entry components to use shared CSS patterns
- Add frontend-style-auditor agent for style consistency checks
- Minor OCR validation and job worker improvements
- Update start-prod.sh configuration

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/shared/styles/layout/header.css

@@ -132,6 +132,42 @@
   background-color: rgba(255, 255, 255, 0.1);
 }
 
+/* Theme Toggle Button */
+.theme-toggle-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 36px;
+  height: 36px;
+  background: transparent;
+  border: 1px solid var(--surface-border, #e2e8f0);
+  border-radius: var(--radius-md, 6px);
+  cursor: pointer;
+  color: var(--text-color, #111827);
+  transition: all 0.15s ease;
+}
+
+.theme-toggle-btn:hover {
+  background: var(--surface-hover, #f1f5f9);
+  border-color: var(--primary-500, #3b82f6);
+  color: var(--primary-500, #3b82f6);
+}
+
+.theme-toggle-btn i {
+  font-size: 1rem;
+}
+
+/* Gradient header theme toggle */
+.header-container--gradient .theme-toggle-btn {
+  color: white;
+  border-color: rgba(255, 255, 255, 0.3);
+}
+
+.header-container--gradient .theme-toggle-btn:hover {
+  background: rgba(255, 255, 255, 0.1);
+  border-color: white;
+}
+
 /* Mobile Responsive */
 @media (max-width: 768px) {
   .header-container {