Add self-hosted usage analytics: pageview tracking + admin stats dashboard

Records pageviews (path, referrer, browser/OS/device, IP, GeoIP country) via
a POST /api/track beacon into a new PageView table, and exposes aggregated
daily/breakdown stats behind a token-gated GET /api/admin/stats endpoint with
brute-force lockout. Frontend gets a /admin dashboard (charts + breakdown
tables) built on recharts, with a switchable per-day pageviews chart.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/vite.config.ts

@@ -40,6 +40,12 @@ export default defineConfig({
         ws: true,
         changeOrigin: true,
       },
+      '/api': {
+        // Backend HTTP endpoints (/api/track, /api/admin/stats) -- kept under
+        // /api so they never collide with client-side routes like /admin/stats.
+        target: process.env.VITE_BACKEND_URL ?? 'http://localhost:5000',
+        changeOrigin: true,
+      },
     },
   },
 });