feat: add GitHub repository dashboard with Prometheus metrics

ghtracker authenticates as a GitHub App and scans a configured list of repositories on a schedule. It serves a dashboard, a JSON state endpoint, a health probe and Prometheus metrics.

The dashboard lists only items that need attention: failing workflows, pull requests that wait too long or fail their checks, stale issues and projects that failed to scan. It has search, dynamic filters and a button that rescans on demand. The Vue app is embedded in the Go binary.

The client protects the GitHub rate limit with conditional requests, a request reserve and Retry-After handling.

Makefile

@@ -0,0 +1,21 @@
+.PHONY: ui build test lint dev
+
+ui:
+	pnpm install --frozen-lockfile
+	pnpm build
+
+build: ui
+	go build -o ghtracker .
+
+test:
+	pnpm test
+	go test -race ./...
+
+lint:
+	pnpm lint
+	pnpm typecheck
+	golangci-lint run ./...
+
+# Run the Go server (config.yaml) and the Vite dev server with hot reload; open http://localhost:5173.
+dev:
+	go run . -config config.yaml & pnpm dev