docs: Update Docker service names to match docker-compose.yml

- Changed gemini-mcp: to zen-mcp: throughout documentation
- Updated gemini-mcp-redis to zen-mcp-redis container references
- Fixed docker compose logs commands to use zen-mcp service name
- Ensures consistency with actual docker-compose.yml service definitions

🤖 Generated with Claude Code

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

docs/contributing/setup.md

@@ -177,7 +177,7 @@ Create `docker-compose.dev.yml`:
 
 ```yaml
 services:
-  gemini-mcp:
+  zen-mcp:
     build:
       context: .
       dockerfile: Dockerfile.dev  # If you have a dev Dockerfile