feat: add CurveEditor component (#8860)

## Summary
Prerequisite for upcoming native color correction nodes (ColorCurves).

Reusable curve editor with monotone cubic Hermite interpolation,
drag-to-add/move/delete control points, and SVG-based rendering.
Includes CurvePoint type, LUT generation utility, and useCurveEditor
composable for interaction logic.

## Screenshots (if applicable)



https://github.com/user-attachments/assets/948352c7-bdf2-40f9-a8f0-35bc2b2f3202

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8860-feat-add-CurveEditor-component-and-d3-shape-dependency-3076d73d3650817f8421f98e349569d0)
by [Unito](https://www.unito.io)

src/schemas/nodeDef/nodeDefSchemaV2.ts

@@ -126,6 +126,15 @@ const zTextareaInputSpec = zBaseInputOptions.extend({
     .optional()
 })
 
+const zCurvePoint = z.tuple([z.number(), z.number()])
+
+const zCurveInputSpec = zBaseInputOptions.extend({
+  type: z.literal('CURVE'),
+  name: z.string(),
+  isOptional: z.boolean().optional(),
+  default: z.array(zCurvePoint).optional()
+})
+
 const zCustomInputSpec = zBaseInputOptions.extend({
   type: z.string(),
   name: z.string(),
@@ -146,6 +155,7 @@ const zInputSpec = z.union([
   zChartInputSpec,
   zGalleriaInputSpec,
   zTextareaInputSpec,
+  zCurveInputSpec,
   zCustomInputSpec
 ])
 
@@ -190,6 +200,7 @@ export type BoundingBoxInputSpec = z.infer<typeof zBoundingBoxInputSpec>
 export type ChartInputSpec = z.infer<typeof zChartInputSpec>
 export type GalleriaInputSpec = z.infer<typeof zGalleriaInputSpec>
 export type TextareaInputSpec = z.infer<typeof zTextareaInputSpec>
+export type CurveInputSpec = z.infer<typeof zCurveInputSpec>
 export type CustomInputSpec = z.infer<typeof zCustomInputSpec>
 
 export type InputSpec = z.infer<typeof zInputSpec>