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/AttentionRow.vue

@@ -0,0 +1,45 @@
+<script setup lang="ts">
+import { computed } from 'vue'
+import { FontAwesomeIcon } from '@fortawesome/vue-fontawesome'
+import AgeMeter from '@/components/AgeMeter.vue'
+import { ageSince, isZeroTime, secondsSince, shorten } from '@/lib/format'
+import { iconFor } from '@/lib/kinds'
+import type { Row } from '@/lib/types'
+
+const props = defineProps<{ row: Row; nowMs: number; critSeconds: number }>()
+
+const ratio = computed(() => secondsSince(props.row.since, props.nowMs) / props.critSeconds)
+</script>
+
+<template>
+  <li class="grid grid-cols-[2rem_minmax(0,1fr)_auto] items-start gap-x-3 py-3" data-test="row">
+    <span
+      class="flex size-8 items-center justify-center rounded-md"
+      :class="row.severity === 'crit' ? 'bg-crit/12 text-crit' : 'bg-warn/12 text-warn'"
+    >
+      <FontAwesomeIcon :icon="iconFor(row.kind)" aria-hidden="true" />
+      <span class="sr-only">{{ row.severity === 'crit' ? 'Critical' : 'Warning' }}</span>
+    </span>
+    <div class="min-w-0">
+      <a
+        :href="row.url"
+        class="hover:text-link leading-snug font-medium wrap-anywhere underline-offset-4 hover:underline"
+      >
+        {{ shorten(row.subject) }}
+      </a>
+      <p class="text-muted-foreground mt-0.5 text-sm wrap-anywhere">
+        {{ shorten(row.detail, 120) }}
+      </p>
+    </div>
+    <div class="flex flex-col items-end gap-1.5 pt-0.5">
+      <span class="text-muted-foreground font-mono text-xs whitespace-nowrap">
+        {{ isZeroTime(row.since) ? '' : ageSince(row.since, nowMs) }}
+      </span>
+      <AgeMeter
+        v-if="row.kind === 'pr_waiting' && !isZeroTime(row.since)"
+        :ratio="ratio"
+        :severity="row.severity"
+      />
+    </div>
+  </li>
+</template>