refactor(frontend): finish shadcn→custom primitive migration (green build)

- Remove tw-animate-css import + dead src/components/ui shadcn tree
- Convert 7 orphaned components (moderation, analysis, guild-selector,
  voice/activity-timeline, shared/empty+error) to new primitives
- Add missing moderation/view.tsx; analysis uses SearchPanel directly
- globals.css now uses new signal-driven ops-console tokens
- tsc --noEmit clean, next build green (11 routes), local smoke 200

services/frontend/src/components/primitives/button.tsx

@@ -0,0 +1,55 @@
+"use client";
+
+import { type HTMLMotionProps, motion, useReducedMotion } from "motion/react";
+import { forwardRef } from "react";
+import { cn } from "@/lib/utils";
+
+type Variant = "primary" | "ghost" | "danger" | "outline";
+type Size = "sm" | "md" | "lg" | "icon";
+
+const variantClass: Record<Variant, string> = {
+  primary:
+    "bg-[var(--color-signal)] text-[var(--color-signal-ink)] hover:opacity-90",
+  ghost:
+    "bg-transparent text-[var(--color-ink)] hover:bg-[var(--color-surface-2)]",
+  danger: "bg-[var(--color-vermilion)] text-white hover:opacity-90",
+  outline:
+    "bg-transparent text-[var(--color-ink)] border border-[var(--color-hairline)] hover:bg-[var(--color-surface-2)]",
+};
+
+const sizeClass: Record<Size, string> = {
+  sm: "h-8 px-3 text-xs rounded-[var(--radius-r-control)]",
+  md: "h-10 px-4 text-sm rounded-[var(--radius-r-control)]",
+  lg: "h-12 px-6 text-base rounded-[var(--radius-r)]",
+  icon: "size-9 rounded-[var(--radius-r-control)]",
+};
+
+export interface ButtonProps extends Omit<HTMLMotionProps<"button">, "ref"> {
+  variant?: Variant;
+  size?: Size;
+}
+
+export const Button = forwardRef<HTMLButtonElement, ButtonProps>(
+  (
+    { className, variant = "primary", size = "md", children, ...props },
+    ref,
+  ) => {
+    const reduce = useReducedMotion();
+    return (
+      <motion.button
+        ref={ref}
+        className={cn(
+          "inline-flex items-center justify-center gap-2 select-none cursor-pointer font-medium outline-none focus-visible:ring-2 focus-visible:ring-[var(--color-ring)] disabled:opacity-50 disabled:pointer-events-none transition-colors duration-150",
+          variantClass[variant],
+          sizeClass[size],
+          className,
+        )}
+        whileTap={reduce ? undefined : { scale: 0.97 }}
+        {...props}
+      >
+        {children}
+      </motion.button>
+    );
+  },
+);
+Button.displayName = "Button";