Update project configuration and documentation

- Modified .gitignore to retain rules directory while excluding other cursor files.
- Updated backend-go.mdc to clarify compatibility notes.
- Enhanced project-conventions.mdc with guidelines on coding practices and running tests.
- Added SKILL.md for detailed instructions on running backend and frontend tests in the hnh-map monorepo.

.cursor/skills/run-tests/SKILL.md

@@ -0,0 +1,53 @@
+---
+name: run-tests
+description: Runs backend (Go) and frontend (Vitest) tests for the hnh-map monorepo. Use when the user asks to run tests, verify tests, or after making code changes that should be validated.
+---
+
+# Run tests
+
+## When to run
+
+- User asks to run tests, run the test suite, or verify tests pass.
+- After implementing or changing code that should be validated by tests.
+
+## What to run
+
+This repo has two test suites. Run the one(s) that match the changed code, or both if unsure.
+
+### Backend (Go)
+
+From repo root:
+
+```bash
+make test
+```
+
+Or:
+
+```bash
+go test ./...
+```
+
+Uses temp dirs and in-memory DBs; no external services needed.
+
+### Frontend (Vitest)
+
+From repo root:
+
+```bash
+npm --prefix frontend-nuxt run test
+```
+
+Or from `frontend-nuxt/`:
+
+```bash
+npm test
+```
+
+## Scope
+
+- **Backend-only changes** (e.g. `internal/`, `cmd/`): run `make test`.
+- **Frontend-only changes** (e.g. `frontend-nuxt/`): run `npm --prefix frontend-nuxt run test`.
+- **Both or unclear**: run backend then frontend.
+
+Report pass/fail and any failing test names or errors.