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/server-reference-manifest.json

@@ -1,5 +0,0 @@
-{
-  "node": {},
-  "edge": {},
-  "encryptionKey": "SwjZ5eoKQ5zrp+xQWYDZCio0rTE23bQaZ8guKGqx2/o="
-}