feat: add SnapIndicator component for timeline snapping visualization

apps/web/src/components/editor/snap-indicator.tsx

@@ -0,0 +1,75 @@
+"use client";
+
+import { SnapPoint } from "@/hooks/use-timeline-snapping";
+import { TIMELINE_CONSTANTS } from "@/constants/timeline-constants";
+
+interface SnapIndicatorProps {
+  snapPoint: SnapPoint | null;
+  zoomLevel: number;
+  timelineHeight: number;
+  isVisible: boolean;
+}
+
+export function SnapIndicator({
+  snapPoint,
+  zoomLevel,
+  timelineHeight,
+  isVisible,
+}: SnapIndicatorProps) {
+  if (!isVisible || !snapPoint) {
+    return null;
+  }
+
+  const leftPosition =
+    snapPoint.time * TIMELINE_CONSTANTS.PIXELS_PER_SECOND * zoomLevel;
+
+  const getIndicatorColor = () => {
+    switch (snapPoint.type) {
+      case "grid":
+        return "bg-blue-400";
+      case "element-start":
+      case "element-end":
+        return "bg-green-400";
+      case "playhead":
+        return "bg-red-400";
+      default:
+        return "bg-gray-400";
+    }
+  };
+
+  const getIndicatorLabel = () => {
+    switch (snapPoint.type) {
+      case "grid":
+        return "Grid";
+      case "element-start":
+        return "Start";
+      case "element-end":
+        return "End";
+      case "playhead":
+        return "Playhead";
+      default:
+        return "";
+    }
+  };
+
+  return (
+    <div
+      className="absolute top-0 pointer-events-none z-50"
+      style={{
+        left: `${leftPosition}px`,
+        height: `${timelineHeight}px`,
+      }}
+    >
+      {/* Snap line */}
+      <div className={`w-0.5 h-full ${getIndicatorColor()} opacity-80`} />
+
+      {/* Snap label */}
+      <div
+        className={`absolute top-0 left-1 px-1 py-0.5 text-xs text-white rounded ${getIndicatorColor()} opacity-90 whitespace-nowrap`}
+        style={{ transform: "translateY(-100%)" }}
+      >
+        {getIndicatorLabel()} ({snapPoint.time.toFixed(1)}s)
+      </div>
+    </div>
+  );
+}