feat(frontend): Kinetic Precision design system — new lime theme, glassmorphism, redesigned pages

- New design system: Stitch (kinetic-precision.css) with lime (#cafd00) accent
- New Google Fonts: Lexend, Plus Jakarta Sans, Space Grotesk
- New page: BenchmarksPage with strength/endurance/body tracking
- Redesigned: Dashboard, ProgressPage, WorkoutPage, LoginPage + LoginPage.css
- Add shared glassmorphism nav, kinetic buttons, intensity indicators
- Build: 265KB JS / 88KB CSS / 2.54s (clean)

scripts/preflight/03-load-test-setup.js

@@ -0,0 +1,20 @@
+import http from 'k6/http';
+import { check, sleep } from 'k6';
+
+export const options = {
+  vus: 10,
+  duration: '1m',
+  thresholds: {
+    http_req_duration: ['p(95)<500', 'p(99)<1000'],
+    http_req_failed: ['rate<0.01'],
+  },
+};
+
+export default function() {
+  const res = http.get('https://gravl-prod.example.com/api/health');
+  check(res, {
+    'status is 200': (r) => r.status === 200,
+    'response time OK': (r) => r.timings.duration < 500,
+  });
+  sleep(1);
+}