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/onboarding/MusclesStep.tsx

@@ -0,0 +1,98 @@
+"use client";
+
+import { useState, useEffect } from "react";
+import { api } from "@/lib/api";
+import { Card } from "@/components/ui/Card";
+import { Spinner } from "@/components/ui/Spinner";
+import type { Muscle } from "@/lib/types";
+
+interface MusclesStepProps {
+  selectedIds: number[];
+  onChange: (ids: number[]) => void;
+}
+
+export function MusclesStep({ selectedIds, onChange }: MusclesStepProps) {
+  const [muscles, setMuscles] = useState<Muscle[]>([]);
+  const [loading, setLoading] = useState(true);
+
+  useEffect(() => {
+    async function fetch() {
+      try {
+        const data = await api.getMuscles();
+        setMuscles(data);
+      } catch (err) {
+        console.error("Failed to fetch muscles:", err);
+      } finally {
+        setLoading(false);
+      }
+    }
+    fetch();
+  }, []);
+
+  const toggle = (id: number) => {
+    if (selectedIds.includes(id)) {
+      onChange(selectedIds.filter((i) => i !== id));
+    } else {
+      onChange([...selectedIds, id]);
+    }
+  };
+
+  if (loading) {
+    return (
+      <div className="flex items-center justify-center py-20">
+        <Spinner size="lg" />
+      </div>
+    );
+  }
+
+  return (
+    <div>
+      <h2 className="text-2xl font-bold text-zinc-100 mb-2">
+        Target Muscles
+      </h2>
+      <p className="text-zinc-400 mb-6">
+        Select the muscle groups you want to focus on. Leave empty to target all
+        muscle groups equally.
+      </p>
+
+      <button
+        type="button"
+        onClick={() => {
+          if (selectedIds.length === muscles.length) {
+            onChange([]);
+          } else {
+            onChange(muscles.map((m) => m.id));
+          }
+        }}
+        className="mb-4 text-sm font-medium text-accent hover:underline"
+      >
+        {selectedIds.length === muscles.length ? "Deselect All" : "Select All"}
+      </button>
+
+      <div className="grid grid-cols-2 sm:grid-cols-3 md:grid-cols-4 gap-3">
+        {muscles.map((muscle) => {
+          const isSelected = selectedIds.includes(muscle.id);
+          return (
+            <Card
+              key={muscle.id}
+              onClick={() => toggle(muscle.id)}
+              className={`p-4 text-center transition-all duration-150 ${
+                isSelected
+                  ? "border-[#39FF14] bg-[rgba(57,255,20,0.1)]"
+                  : ""
+              }`}
+            >
+              <span
+                className={`text-sm font-medium ${
+                  isSelected ? "text-accent" : "text-zinc-100"
+                }`}
+              >
+                {muscle.name}
+              </span>
+            </Card>
+          );
+        })}
+      </div>
+    </div>
+  );
+}