fix: remove .next build artifacts from git tracking

- Add .next to .gitignore to prevent future conflicts
- Remove all build artifacts from git tracking
- Focus on source code changes only for cleaner merges

.next/server/app-paths-manifest.json

@@ -1,6 +0,0 @@
-{
-  "/page": "app/page.js",
-  "/favicon.ico/route": "app/favicon.ico/route.js",
-  "/contact/page": "app/contact/page.js",
-  "/_not-found/page": "app/_not-found/page.js"
-}