feat(compliance): add time-based trend charts to Compliance page

Add 6 Recharts charts in a collapsible Historical Trends panel on the
Compliance page, covering all Tier-1 recommendations from the reporting
design doc.

Backend — 5 new API endpoints:
  - GET /api/compliance/trends        — active totals + per-team counts per upload
  - GET /api/compliance/mttr          — mean days to resolution per team
  - GET /api/compliance/top-recurring — most persistent active findings by seen_count
  - GET /api/compliance/category-trend — category breakdown per upload (future use)
  - GET /api/archer-tickets/status-trend — ticket pipeline by creation date + status

Frontend — new ComplianceChartsPanel component:
  - Active Findings Over Time (multi-line: total + per-team dashed)
  - Change per Report Cycle (stacked bar: new/recurring + resolved)
  - Team Compliance Health (multi-line per team)
  - Mean Time to Resolution (horizontal bar per team)
  - Most Persistent Findings (horizontal bar top-10 by seen_count)
  - Archer Exception Pipeline (stacked bar by date + status)

All charts degrade gracefully to a no-data placeholder until uploads
accumulate. Panel is collapsible to stay out of the way when not needed.
Adds recharts dependency to frontend.

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

backend/routes/archerTickets.js

@@ -217,6 +217,25 @@ function createArcherTicketsRouter(db) {
     });
   });
 
+  // GET /status-trend — ticket counts grouped by creation date + status
+  // Used for time-based Archer pipeline chart on the Compliance page.
+  router.get('/status-trend', requireAuth(db), (req, res) => {
+    db.all(
+      `SELECT DATE(created_at) AS date, status, COUNT(*) AS count
+       FROM archer_tickets
+       GROUP BY DATE(created_at), status
+       ORDER BY date ASC`,
+      [],
+      (err, rows) => {
+        if (err) {
+          console.error('Error fetching Archer status trend:', err);
+          return res.status(500).json({ error: 'Internal server error.' });
+        }
+        res.json({ statusTrend: rows });
+      }
+    );
+  });
+
   return router;
 }