feat: Add photo management features, duplicate detection, attempt limits, and admin deletion

- Add duplicate photo detection (file hash and URL checking)
- Add max attempts per photo with UI counter
- Simplify penalty system (auto-enable when points > 0)
- Prevent scores from going below 0
- Add admin photo deletion functionality
- Improve navigation with always-visible logout
- Prevent users from guessing their own photos

jest.setup.js

@@ -0,0 +1,39 @@
+// Learn more: https://github.com/testing-library/jest-dom
+import '@testing-library/jest-dom'
+
+// Polyfill for TextEncoder/TextDecoder
+import { TextEncoder, TextDecoder } from 'util'
+global.TextEncoder = TextEncoder
+global.TextDecoder = TextDecoder
+
+// Mock Next.js router
+jest.mock('next/navigation', () => ({
+  useRouter() {
+    return {
+      push: jest.fn(),
+      replace: jest.fn(),
+      prefetch: jest.fn(),
+      back: jest.fn(),
+      pathname: '/',
+      query: {},
+      asPath: '/',
+    }
+  },
+  usePathname() {
+    return '/'
+  },
+  useSearchParams() {
+    return new URLSearchParams()
+  },
+}))
+
+// Mock next-auth/react
+jest.mock('next-auth/react', () => ({
+  useSession: jest.fn(() => ({
+    data: null,
+    status: 'unauthenticated',
+  })),
+  signIn: jest.fn(),
+  signOut: jest.fn(),
+  SessionProvider: ({ children }) => children,
+}))