refactor: extract timeline model types

Move project entity shapes into the model layer so sibling domains no longer depend on timeline for core data types.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/web/src/model/elements/image.ts

@@ -0,0 +1,15 @@
+import type { Effect } from "@/effects/types";
+import type { Mask } from "@/masks/types";
+import type { BlendMode, Transform } from "@/rendering";
+import type { BaseTimelineElement } from "./base";
+
+export interface ImageElement extends BaseTimelineElement {
+	type: "image";
+	mediaId: string;
+	hidden?: boolean;
+	transform: Transform;
+	opacity: number;
+	blendMode?: BlendMode;
+	effects?: Effect[];
+	masks?: Mask[];
+}