Enhance development workflow with Docker integration

- Updated CONTRIBUTING.md to clarify the use of Makefile targets for running tasks inside Docker, eliminating the need for local Go or Node installations.
- Introduced docker-compose.tools.yml for backend and frontend tools, allowing for streamlined testing, linting, and formatting.
- Created Dockerfile.tools to set up a Go environment with necessary tools for testing and linting.
- Modified Makefile to include separate targets for backend and frontend tests, improving clarity and usability.
- Updated documentation in development.md and testing.md to reflect the new Docker-based workflow for running tests and development tasks.

docs/testing.md

@@ -2,13 +2,24 @@
 
 ## Running tests
 
-### Backend (Go)
+The canonical way to run tests is via Docker (no local Go or Node required):
 
 ```bash
 make test
 ```
 
-Or directly:
+This runs both backend and frontend tests in Docker. For one side only:
+
+```bash
+make test-backend   # Go tests only
+make test-frontend # Vitest only
+```
+
+### Backend (Go)
+
+With Docker (recommended): `make test-backend` or `make test`.
+
+Or directly if you have Go installed:
 
 ```bash
 go test ./...
@@ -16,6 +27,10 @@ go test ./...
 
 ### Frontend (Vitest)
 
+With Docker (recommended): `make test-frontend` or `make test`.
+
+Or directly if you have Node installed:
+
 ```bash
 cd frontend-nuxt
 npm test