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.

src/components/RepoGroup.vue

@@ -0,0 +1,41 @@
+<script setup lang="ts">
+import { faTag } from '@fortawesome/free-solid-svg-icons'
+import { FontAwesomeIcon } from '@fortawesome/vue-fontawesome'
+import AttentionRow from '@/components/AttentionRow.vue'
+import { Badge } from '@/components/ui/badge'
+import type { Block } from '@/lib/types'
+
+defineProps<{ block: Block; nowMs: number; critSeconds: number }>()
+</script>
+
+<template>
+  <section class="border-border bg-surface rounded-lg border" data-test="repo-block">
+    <header class="border-border flex flex-wrap items-center gap-x-3 gap-y-1 border-b px-4 py-3">
+      <h3 class="font-semibold">
+        <a :href="block.repo.url" class="hover:text-link underline-offset-4 hover:underline">
+          <span class="text-muted-foreground font-normal"
+            >{{ block.repo.fullName.split('/')[0] }}/</span
+          >{{ block.repo.fullName.split('/')[1] }}
+        </a>
+      </h3>
+      <Badge v-if="block.repo.release" variant="secondary" as-child class="font-mono">
+        <a :href="block.repo.release.url">
+          <FontAwesomeIcon :icon="faTag" aria-hidden="true" class="text-[0.7em]" />
+          {{ block.repo.release.tag }}
+        </a>
+      </Badge>
+      <span class="text-muted-foreground ml-auto text-xs">
+        {{ block.rows.length }} {{ block.rows.length === 1 ? 'item' : 'items' }}
+      </span>
+    </header>
+    <ul class="divide-border divide-y px-4">
+      <AttentionRow
+        v-for="row in block.rows"
+        :key="row.url"
+        :row="row"
+        :now-ms="nowMs"
+        :crit-seconds="critSeconds"
+      />
+    </ul>
+  </section>
+</template>