Server: HTML dashboard at /dashboard showing all sites + session history

Browsable at /dashboard — authenticates via ?key=<api_key> once per browser
session (stored in a PHP session cookie). Lists all sites ordered by most-
recently-active, with session counts and in-progress badge. Click any site
to see its full healthcheck history with dates and durations.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/src/Store.php

@@ -176,4 +176,42 @@ final class Store {
         $rows = $stmt->fetchAll();
         return array_map(static fn($r) => ['site_key' => $r['site_key'], 'last_seen' => (int) $r['last_seen']], $rows);
     }
+
+    /**
+     * Summary of all sites for the dashboard: one row per site_key,
+     * ordered by most-recently-active first.
+     * @return array<int, array{site_key:string, total:int, finished:int, last_started_at:int, last_finished_at:int|null, last_reporting_url:string}>
+     */
+    public static function allSitesSummary(): array {
+        $stmt = Db::pdo()->query(
+            'SELECT
+                site_key,
+                COUNT(*)                                        AS total,
+                SUM(CASE WHEN finished_at IS NOT NULL THEN 1 ELSE 0 END) AS finished,
+                MAX(started_at)                                 AS last_started_at
+             FROM healthchecks
+             GROUP BY site_key
+             ORDER BY MAX(updated_at) DESC'
+        );
+        $rows = $stmt->fetchAll();
+        // Fetch the reporting_url and finished_at from the most recent session per site.
+        $out = [];
+        foreach ($rows as $r) {
+            $detail = Db::pdo()->prepare(
+                'SELECT reporting_url, finished_at FROM healthchecks
+                 WHERE site_key = ? ORDER BY started_at DESC LIMIT 1'
+            );
+            $detail->execute([$r['site_key']]);
+            $last = $detail->fetch() ?: [];
+            $out[] = [
+                'site_key'         => (string) $r['site_key'],
+                'total'            => (int) $r['total'],
+                'finished'         => (int) $r['finished'],
+                'last_started_at'  => (int) $r['last_started_at'],
+                'last_finished_at' => isset($last['finished_at']) && $last['finished_at'] !== null ? (int) $last['finished_at'] : null,
+                'last_reporting_url' => (string) ($last['reporting_url'] ?? ''),
+            ];
+        }
+        return $out;
+    }
 }