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.

deploy/kubernetes/externalsecret.yaml

@@ -0,0 +1,16 @@
+apiVersion: external-secrets.io/v1
+kind: ExternalSecret
+metadata:
+  name: ghtracker-github-app
+spec:
+  refreshInterval: 24h
+  secretStoreRef:
+    name: secrets # your ClusterSecretStore
+    kind: ClusterSecretStore
+  target:
+    name: ghtracker-github-app
+    creationPolicy: Owner
+  data:
+    - secretKey: GHTRACKER_PRIVATE_KEY
+      remoteRef:
+        key: ghtracker/app_private_key # where you keep the App private key