Remove next-view-transitions and use native View Transition API

- Remove external next-view-transitions dependency
- Use Next.js 16 native navigation and Safari 18+ native View Transition API
- Add ViewTransitionProvider for minimal wrapping with Safari 18+ detection
- Updated all Link imports from external package to next/link
- Removed link-wrapper.tsx and view-transitions-wrapper.tsx

This resolves Safari compatibility issues while maintaining transitions on modern browsers.

components/back-to-top.tsx

@@ -28,7 +28,7 @@ export function BackToTop() {
         window.scrollTo({ top: 0, behavior: 'smooth' });
       }}
       aria-label="回到頁面頂部"
-      className="fixed bottom-6 right-4 z-40 inline-flex h-9 w-9 items-center justify-center rounded-full bg-slate-900 text-slate-50 shadow-md ring-1 ring-slate-800/70 transition hover:bg-slate-700 dark:bg-slate-100 dark:text-slate-900 dark:ring-slate-300/70 dark:hover:bg-slate-300"
+       className="fixed bottom-6 right-4 z-40 inline-flex h-9 w-9 items-center justify-center rounded-full bg-accent text-white shadow-lg ring-2 ring-accent/30 transition-all duration-300 ease-out-expo hover:-translate-y-1 hover:shadow-xl focus-visible:outline-none focus-visible:ring-4 focus-visible:ring-accent/40 dark:bg-accent dark:ring-accent/30 dark:hover:bg-accent/90"
     >
       <span className="text-lg leading-none">↑</span>
     </button>