Add configuration files and update project documentation

- Introduced .editorconfig for consistent coding styles across the project.
- Added .golangci.yml for Go linting configuration.
- Updated AGENTS.md to clarify project structure and components.
- Enhanced CONTRIBUTING.md with Makefile usage for common tasks.
- Updated Dockerfiles to use Go 1.24 and improved build instructions.
- Refined README.md and deployment documentation for clarity.
- Added testing documentation in testing.md for backend and frontend tests.
- Introduced Makefile for streamlined development commands and tasks.

docs/testing.md

@@ -0,0 +1,89 @@
+# Testing
+
+## Running tests
+
+### Backend (Go)
+
+```bash
+make test
+```
+
+Or directly:
+
+```bash
+go test ./...
+```
+
+### Frontend (Vitest)
+
+```bash
+cd frontend-nuxt
+npm test
+```
+
+The frontend uses [Vitest](https://vitest.dev/) with `happy-dom` as the test environment. Configuration is in `frontend-nuxt/vitest.config.ts`.
+
+## Test structure
+
+### Backend
+
+Tests use the standard `testing` package with table-driven tests. Each test creates a temporary bbolt database via `t.TempDir()` so tests are fully isolated and require no external dependencies.
+
+| File | What it covers |
+|------|---------------|
+| `internal/app/app_test.go` | Domain types (`Coord.Name`, `Coord.Parent`, `Auths.Has`), `Topic` pub/sub |
+| `internal/app/migrations_test.go` | Migration on fresh DB, idempotency, version tracking |
+| `internal/app/store/db_test.go` | All store CRUD operations (users, sessions, tokens, config, maps, grids, tiles, markers, OAuth states), context cancellation, edge cases |
+| `internal/app/services/auth_test.go` | Login, session management, token validation, password changes, OAuth bootstrap |
+| `internal/app/services/admin_test.go` | User CRUD, settings, map management, wipe |
+| `internal/app/services/map_test.go` | Map data retrieval, characters, markers, tiles, config, grid storage, SSE watchers |
+| `internal/app/services/client_test.go` | Content-type fix helper |
+| `internal/app/handlers/handlers_test.go` | HTTP integration tests for all API endpoints using `httptest` (auth, admin, map data, error handling) |
+
+### Frontend
+
+Frontend tests are located alongside the source code in `__tests__/` directories:
+
+| File | What it covers |
+|------|---------------|
+| `frontend-nuxt/composables/__tests__/useMapApi.test.ts` | Map API composable |
+| `frontend-nuxt/composables/__tests__/useMapLogic.test.ts` | Map logic composable |
+| `frontend-nuxt/composables/__tests__/useAppPaths.test.ts` | Application path helpers |
+| `frontend-nuxt/lib/__tests__/Character.test.ts` | Character lib |
+| `frontend-nuxt/lib/__tests__/Marker.test.ts` | Marker lib |
+| `frontend-nuxt/lib/__tests__/UniqueList.test.ts` | UniqueList utility |
+
+Nuxt auto-imports are mocked via `frontend-nuxt/__mocks__/nuxt-imports.ts` and the `#imports` alias in the Vitest config.
+
+## Writing new tests
+
+### Backend conventions
+
+- Use table-driven tests where multiple input/output pairs make sense.
+- Create a temporary database with `t.TempDir()` and `bbolt.Open()` for isolation.
+- Use `t.Helper()` in test helper functions.
+- Use `t.Cleanup()` to close the database after the test.
+
+Example pattern:
+
+```go
+func TestMyFeature(t *testing.T) {
+    dir := t.TempDir()
+    db, err := bbolt.Open(filepath.Join(dir, "test.db"), 0600, nil)
+    if err != nil {
+        t.Fatal(err)
+    }
+    t.Cleanup(func() { db.Close() })
+
+    st := store.New(db)
+    // ... test logic ...
+}
+```
+
+For handler tests, use `httptest.NewRecorder()` and `httptest.NewRequest()` to simulate HTTP requests without starting a real server.
+
+### Frontend conventions
+
+- Place tests in `__tests__/` directories next to the source files.
+- Name test files `<source-name>.test.ts`.
+- Use Vitest globals (`describe`, `it`, `expect`).