feat: add color system panel, eyedropper tool, and color swatch components

Color panel with foreground/background swatches, react-colorful picker
popover, HEX/RGB/HSL input modes, recent colors row, swap (X) and reset (D).
Eyedropper tool samples composited pixels via stage.toCanvas() with 1x1/3x3/5x5
sample size options, alt+click for background color.

apps/web/src/components/editor/common/color-swatch.tsx

@@ -0,0 +1,63 @@
+// apps/web/src/components/editor/common/color-swatch.tsx
+
+import { cn } from "@/lib/utils";
+
+type SwatchSize = "sm" | "md" | "lg";
+
+const SIZE_CLASSES: Record<SwatchSize, string> = {
+  sm: "w-5 h-5",
+  md: "w-7 h-7",
+  lg: "w-9 h-9",
+};
+
+// Checkerboard pattern for transparent colors
+const CHECKERBOARD =
+  "repeating-conic-gradient(rgba(128,128,128,0.3) 0% 25%, transparent 0% 50%) 0 0 / 8px 8px";
+
+interface ColorSwatchProps {
+  color: string;
+  size?: SwatchSize;
+  active?: boolean;
+  showBorder?: boolean;
+  onClick?: () => void;
+  className?: string;
+  label?: string;
+  "data-testid"?: string;
+}
+
+export function ColorSwatch({
+  color,
+  size = "md",
+  active,
+  showBorder = true,
+  onClick,
+  className,
+  label,
+  ...dataProps
+}: ColorSwatchProps) {
+  const isTransparent = color === "transparent" || color.length === 9;
+
+  return (
+    <button
+      type="button"
+      title={label ?? color}
+      aria-label={label ?? `Color ${color}`}
+      onClick={onClick}
+      className={cn(
+        "relative rounded transition-shadow shrink-0",
+        SIZE_CLASSES[size],
+        showBorder && "border border-border",
+        active && "ring-2 ring-primary ring-offset-1 ring-offset-card",
+        onClick && "cursor-pointer hover:ring-1 hover:ring-primary/50",
+        !onClick && "cursor-default",
+        className,
+      )}
+      style={{
+        background: isTransparent ? CHECKERBOARD : undefined,
+      }}
+      {...dataProps}
+    >
+      <span className="absolute inset-0 rounded" style={{ backgroundColor: color }} />
+    </button>
+  );
+}