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/AttentionList.vue

@@ -0,0 +1,56 @@
+<script setup lang="ts">
+import { faCircleCheck } from '@fortawesome/free-solid-svg-icons'
+import { FontAwesomeIcon } from '@fortawesome/vue-fontawesome'
+import { ref } from 'vue'
+import FilterBar from '@/components/FilterBar.vue'
+import RepoGroup from '@/components/RepoGroup.vue'
+import type { Facets, Filters } from '@/lib/filters'
+import type { Block } from '@/lib/types'
+
+defineProps<{
+  blocks: Block[]
+  nowMs: number
+  critSeconds: number
+  facets: Facets
+  owners: string[]
+  active: number
+}>()
+const filters = defineModel<Filters>('filters', { required: true })
+defineEmits<{ clear: [] }>()
+
+const bar = ref<InstanceType<typeof FilterBar> | null>(null)
+defineExpose({ focusSearch: () => bar.value?.focus() })
+</script>
+
+<template>
+  <section aria-labelledby="attention-title">
+    <h2 id="attention-title" class="mb-4 text-lg font-semibold tracking-tight">Needs attention</h2>
+    <FilterBar
+      ref="bar"
+      v-model:filters="filters"
+      :facets="facets"
+      :owners="owners"
+      :active="active"
+      class="mb-5"
+      @clear="$emit('clear')"
+    />
+
+    <div
+      v-if="blocks.length === 0"
+      class="border-border text-muted-foreground flex items-center gap-3 rounded-lg border border-dashed p-6"
+      data-test="empty"
+    >
+      <FontAwesomeIcon :icon="faCircleCheck" class="text-ok text-xl" aria-hidden="true" />
+      Nothing matches the current filters.
+    </div>
+    <div v-else class="flex flex-col gap-4">
+      <RepoGroup
+        v-for="block in blocks"
+        :key="block.repo.fullName"
+        :block="block"
+        :now-ms="nowMs"
+        :crit-seconds="critSeconds"
+      />
+    </div>
+  </section>
+</template>