workout generator audit: rules engine, structure rules, split patterns, injury UX, metadata cleanup

- Add rules_engine.py with quantitative rules for all 8 workout types
- Add quality gate retry loop in generate_single_workout()
- Expand calibrate_structure_rules to all 120 combinations (8 types × 5 goals × 3 sections)
- Wire WeeklySplitPattern DB records into _pick_weekly_split()
- Enforce movement patterns from WorkoutStructureRule in exercise selection
- Add straight-set strength support (single main lift, 4-6 rounds)
- Add modality consistency check for duration-dominant workout types
- Add InjuryStep component to onboarding and preferences
- Add sibling exercise exclusion in regenerate and preview_day endpoints
- Display generator warnings on dashboard
- Expand fix_rep_durations, fix_exercise_flags, fix_movement_pattern_typo
- Add audit_exercise_data and check_rules_drift management commands
- Add Next.js frontend with dashboard, onboarding, preferences, history pages
- Add generator app with ML-powered workout generation pipeline
- 96 new tests across 7 test modules

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

werkout-frontend/components/auth/AuthGuard.tsx

@@ -0,0 +1,35 @@
+"use client";
+
+import { useEffect, type ReactNode } from "react";
+import { useRouter } from "next/navigation";
+import { useAuth } from "@/lib/auth";
+import { Spinner } from "@/components/ui/Spinner";
+
+interface AuthGuardProps {
+  children: ReactNode;
+}
+
+export function AuthGuard({ children }: AuthGuardProps) {
+  const { user, loading } = useAuth();
+  const router = useRouter();
+
+  useEffect(() => {
+    if (!loading && !user) {
+      router.replace("/login");
+    }
+  }, [loading, user, router]);
+
+  if (loading) {
+    return (
+      <div className="flex items-center justify-center min-h-screen">
+        <Spinner size="lg" />
+      </div>
+    );
+  }
+
+  if (!user) {
+    return null;
+  }
+
+  return <>{children}</>;
+}