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/ui/Button.tsx

@@ -0,0 +1,69 @@
+"use client";
+
+import { forwardRef, type ButtonHTMLAttributes, type ReactNode } from "react";
+import { Spinner } from "@/components/ui/Spinner";
+
+type Variant = "primary" | "secondary" | "danger" | "ghost";
+type Size = "sm" | "md" | "lg";
+
+interface ButtonProps extends ButtonHTMLAttributes<HTMLButtonElement> {
+  variant?: Variant;
+  size?: Size;
+  loading?: boolean;
+  children: ReactNode;
+}
+
+const variantClasses: Record<Variant, string> = {
+  primary:
+    "bg-accent text-black font-bold hover:bg-accent-hover active:bg-accent-hover",
+  secondary: "bg-zinc-700 text-zinc-100 hover:bg-zinc-600 active:bg-zinc-500",
+  danger: "bg-red-500 text-white hover:bg-red-600 active:bg-red-700",
+  ghost: "bg-transparent text-zinc-100 hover:bg-zinc-800 active:bg-zinc-700",
+};
+
+const sizeClasses: Record<Size, string> = {
+  sm: "px-3 py-1.5 text-sm rounded-lg",
+  md: "px-5 py-2.5 text-base rounded-lg",
+  lg: "px-7 py-3.5 text-lg rounded-xl",
+};
+
+const Button = forwardRef<HTMLButtonElement, ButtonProps>(
+  (
+    {
+      variant = "primary",
+      size = "md",
+      loading = false,
+      disabled,
+      className = "",
+      children,
+      ...rest
+    },
+    ref
+  ) => {
+    const isDisabled = disabled || loading;
+
+    return (
+      <button
+        ref={ref}
+        disabled={isDisabled}
+        className={`
+          inline-flex items-center justify-center gap-2 font-medium
+          transition-colors duration-150 ease-in-out
+          ${variantClasses[variant]}
+          ${sizeClasses[size]}
+          ${isDisabled ? "opacity-50 cursor-not-allowed" : "cursor-pointer"}
+          ${className}
+        `}
+        {...rest}
+      >
+        {loading && <Spinner size="sm" />}
+        {children}
+      </button>
+    );
+  }
+);
+
+Button.displayName = "Button";
+
+export { Button };
+export type { ButtonProps };