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.

CONTRIBUTING.md

@@ -25,19 +25,19 @@ The backend follows a layered architecture: **Store → Services → Handlers**.
 
 ## Formatting, linting, and tests
 
-Use Makefile targets for common tasks:
+Use Makefile targets; they run inside Docker via `docker-compose.tools.yml`, so you do not need Go or Node installed for these tasks:
 
 ```bash
 make fmt      # Format all code (Go + frontend)
 make lint     # Run Go linter (golangci-lint) and frontend ESLint
-make test     # Run Go tests
+make test     # Run backend and frontend tests
 ```
 
-Or run manually:
+Or run manually on the host if you have Go and Node:
 
 - Go: `go fmt ./...` and `golangci-lint run`
 - Frontend: `npm --prefix frontend-nuxt run lint` and `npm --prefix frontend-nuxt run format`
-- Tests: `go test ./...`
+- Tests: `go test ./...` and `npm --prefix frontend-nuxt run test`
 
 Always format and lint before committing. Add or update tests if you change behaviour.