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/configmap.yaml

@@ -0,0 +1,20 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: ghtracker
+data:
+  config.yaml: |
+    listen: ":8080"
+    refresh_interval: 6h
+    github:
+      app_id: 123456 # your GitHub App ID
+      installation_id: 0
+    thresholds:
+      pr_warn_after: 48h
+      pr_crit_after: 168h
+      issue_stale_after: 720h
+      workflow_stuck_after: 6h
+    repos:
+      - lukaszraczylo/kubemirror
+      - lukaszraczylo/semver-generator
+      - lukaszraczylo/traefikoidc