fix: resolve hydration mismatch error and improve project setup

- Fix React hydration mismatch in ThemeProvider with mounted state check
- Update layout.tsx to use light theme by default instead of system
- Optimize photo filtering with useMemo in page.tsx
- Add Express mock API for development
- Update CLAUDE.md with comprehensive project documentation
- Create backend/ and admin/ directories for future development

frontend/package.json

@@ -45,8 +45,10 @@
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "cmdk": "1.0.4",
+    "cors": "^2.8.5",
     "date-fns": "4.1.0",
     "embla-carousel-react": "8.5.1",
+    "express": "^5.1.0",
     "input-otp": "1.4.1",
     "lucide-react": "^0.454.0",
     "next": "15.2.4",