Add bundle analyzer configuration

Configure @next/bundle-analyzer for production bundle analysis:

**Changes:**
- Install @next/bundle-analyzer package
- Update next.config.mjs to wrap config with bundle analyzer
- Add npm script `build:analyze` to run build with ANALYZE=true
- Bundle analyzer only enabled when ANALYZE=true environment variable is set

**Usage:**
```bash
# Run build with bundle analysis
npm run build:analyze

# Opens interactive bundle visualization in browser
# Shows chunk sizes, module dependencies, and optimization opportunities
```

**Note:** Kept Mastodon feed as Client Component (not Server Component)
because formatRelativeTime() uses `new Date()` which requires dynamic
rendering. Converting to Server Component would prevent static generation.

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

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

next.config.mjs

@@ -1,3 +1,9 @@
+import bundleAnalyzer from '@next/bundle-analyzer';
+
+const withBundleAnalyzer = bundleAnalyzer({
+  enabled: process.env.ANALYZE === 'true',
+});
+
 /** @type {import('next').NextConfig} */
 const nextConfig = {
   // Image optimization configuration
@@ -35,4 +41,4 @@ const nextConfig = {
   },
 };
 
-export default nextConfig;
+export default withBundleAnalyzer(nextConfig);