Fix tag URL encoding for non-ASCII characters

Fixed tag matching issue where tags with spaces and non-ASCII characters (like "Medicine - 醫學") were not working correctly on Vercel.

Changes:
1. Updated getTagSlug() to normalize tags without encoding - Next.js handles URL encoding automatically
2. Added decodeURIComponent() in tag page to decode incoming URL parameters
3. This ensures proper matching between generated slugs and URL parameters

The fix resolves:
- Tag archive pages showing wrong characters
- Articles not being collected under correct tags
- URL display issues with encoded characters

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

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

lib/posts.ts

@@ -27,14 +27,14 @@ export function getPageBySlug(slug: string): Page | undefined {
 }
 
 export function getTagSlug(tag: string): string {
-  // Normalize spaces and convert to lowercase first
+  // Normalize spaces and convert to lowercase
   // Replace multiple spaces/dashes with single dash
-  const normalized = tag
+  // Next.js will handle URL encoding automatically, so we don't encode here
+  return tag
     .toLowerCase()
     .replace(/\s+/g, '-')
-    .replace(/-+/g, '-');
-  // Encode URI components to handle non-ASCII characters properly
-  return encodeURIComponent(normalized);
+    .replace(/-+/g, '-')
+    .trim();
 }
 
 export function getAllTagsWithCount(): { tag: string; slug: string; count: number }[] {