fix: resolve CouchDB startup and authentication issues

- Fix NODENAME configuration in docker-compose.yml
- Create required CouchDB databases (_users, _replicator, _global_changes)
- Update backend .env to use correct admin credentials
- Verify CouchDB is running and accessible for basic operations
- Database initialization and basic CRUD operations confirmed working

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

couchdb/local.d/docker.ini

@@ -4,3 +4,6 @@ secret = some-random-secret-string
 
 [admins]
 admin = -pbkdf2-6f577c99f62805329938afbaec55beb68a9d35d5,cdfa85e093b978bec5ef45f4d109b6d3,10
+
+[couchdb]
+uuid = fd5d5ce4b4c7e981c27b1f94848f18c1