feat: promote studio theme to default, add favicon, deep-linkable lightbox

- Studio aesthetic now the default dark/light theme
- Removed MonochromToggle and 3-way theme cycle
- Light mode uses warm Studio-toned palette
- Added favicon (icon.png, apple-touch-icon, PWA icons)
- Lightbox URL sync: #photo-N hash for shareable photo links
- Browser back closes lightbox, shared links open directly

components/ThemeToggle.tsx

@@ -41,7 +41,7 @@ function applyTheme(theme: Theme) {
 // Initialize from localStorage on module load (client-side only)
 if (typeof window !== 'undefined') {
   const stored = localStorage.getItem('theme') as Theme | null;
-  currentTheme = stored || 'dark';
+  currentTheme = stored === 'light' ? 'light' : 'dark';
   document.documentElement.setAttribute('data-theme', currentTheme);
 }