Add GET /api/admin/scraper/history endpoint with pagination

Implement the scraper history endpoint that returns past scrape run
records from the scraper_runs collection. Features include:

- GET /api/admin/scraper/history protected by requireAuth + requireAdmin
- Pagination via limit (1-100, default 30) and offset (default 0) params
- Input validation returning 400 for invalid limit/offset values
- Results sorted by startedAt descending (newest first)
- Graceful error handling returning 503 on database failures
- 20 new tests covering auth, pagination, validation, and error cases

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

routes/admin.js

@@ -1250,5 +1250,55 @@ router.get('/scraper/status', async (req, res) => {
   }
 });
 
+/**
+ * GET /api/admin/scraper/history
+ * Get scraper run history with pagination
+ *
+ * Query params:
+ *   - limit: Number of records (1-100, default 30)
+ *   - offset: Number of records to skip (default 0)
+ */
+router.get('/scraper/history', async (req, res) => {
+  try {
+    const db = req.app.locals.db;
+
+    // Parse and validate pagination parameters
+    let limit = parseInt(req.query.limit);
+    let offset = parseInt(req.query.offset);
+
+    // Validate limit
+    if (req.query.limit !== undefined) {
+      if (isNaN(limit) || limit < 1) {
+        return res.status(400).json({ error: 'Limit must be between 1 and 100' });
+      }
+      limit = Math.min(limit, 100);
+    } else {
+      limit = 30;
+    }
+
+    // Validate offset
+    if (req.query.offset !== undefined) {
+      if (isNaN(offset) || offset < 0) {
+        return res.status(400).json({ error: 'Invalid offset parameter' });
+      }
+    } else {
+      offset = 0;
+    }
+
+    const history = await db.collection(scraperConfig.COLLECTIONS.SCRAPER_RUNS)
+      .find({})
+      .sort({ startedAt: -1 })
+      .skip(offset)
+      .limit(limit)
+      .toArray();
+
+    res.json({ data: history });
+
+  } catch (error) {
+    console.error('Error fetching scraper history:', error);
+    res.status(503).json({ error: 'Service temporarily unavailable' });
+  }
+});
+
 module.exports = router;
 module.exports.clearStatsCache = clearStatsCache;