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/ui/table/Table.vue

@@ -0,0 +1,16 @@
+<script setup lang="ts">
+import type { HTMLAttributes } from 'vue'
+import { cn } from '@/lib/utils'
+
+const props = defineProps<{
+  class?: HTMLAttributes['class']
+}>()
+</script>
+
+<template>
+  <div data-slot="table-container" class="relative w-full overflow-auto">
+    <table data-slot="table" :class="cn('w-full caption-bottom text-sm', props.class)">
+      <slot />
+    </table>
+  </div>
+</template>