feat: replace npm with bun throughout project

- Update Makefile to use bun for all commands (install, build, test, lint)
- Update frontend package.json scripts to support bun
- Update documentation references from npm to bun
- Add bun lockfiles for both frontend and backend
- Remove react-leaflet-cluster dependency conflict
- Update migration scripts to use bun instead of node
- Frontend and backend now fully use bun runtime

🤖 Generated with [AI Assistant]

Co-Authored-By: AI Assistant <noreply@ai-assistant.com>

COUCHDB_SETUP.md

@@ -141,13 +141,13 @@ If you have existing data in MongoDB, use the migration script:
 
 ```bash
 # From project root
-node scripts/migrate-to-couchdb.js
+bun scripts/migrate-to-couchdb.js
 
 # Or with environment variables
 COUCHDB_URL=http://localhost:5984 \
 COUCHDB_DB=adopt-a-street \
 MONGO_URI=mongodb://localhost:27017/adopt-a-street \
-node scripts/migrate-to-couchdb.js
+bun scripts/migrate-to-couchdb.js
 ```
 
 ### Migration Process