feat: introduce WebGL effects system and Blur effect

This implements the foundational architecture for video effects, starting with a multi-pass WebGL rendering pipeline and a customizable Gaussian Blur effect.

Key changes:
- WebGL Engine: Added `raw-loader` for `.glsl` shaders, multi-pass framebuffer rendering, and live offscreen canvas previews.
- Node Architecture: Replaced hardcoded background blur with `CompositeEffectNode` and added `EffectLayerNode` to apply effects to specific visual elements.
- Timeline & DND: Added a new `effect` track type. Upgraded drag-and-drop to support dropping effects directly onto the timeline. Consolidated track constants into a cleaner `TRACK_CONFIG`.
- UI/UX: Added an Effects tab in the assets panel with live previews. Added an Effect Properties panel with sliders and inputs for fine-tuning parameters.
- Data Model: Added `sourceDuration` to video and audio elements, and wrote a v8 storage migration to update existing projects to the new schema.
- Docs: Added `CHANGELOG.md` tracking v0.1.0 and v0.2.0, plus `docs/effects-renderer.md` to document the new WebGL pipeline.

apps/web/src/lib/effects/definitions/blur.ts

@@ -0,0 +1,50 @@
+import type { EffectDefinition } from "@/types/effects";
+import blurFragmentShader from "./blur.frag.glsl";
+
+export const blurEffectDefinition: EffectDefinition = {
+	type: "blur",
+	name: "Blur",
+	keywords: ["blur", "soft", "defocus"],
+	params: [
+		{
+			key: "intensity",
+			label: "Intensity",
+			type: "number",
+			default: 15,
+			min: 0,
+			max: 100,
+			step: 1,
+		},
+	],
+	renderer: {
+		type: "webgl",
+		passes: [
+			{
+				fragmentShader: blurFragmentShader,
+				uniforms: ({ effectParams }) => {
+					const intensity =
+						typeof effectParams.intensity === "number"
+							? effectParams.intensity
+							: Number.parseFloat(String(effectParams.intensity));
+					return {
+						u_sigma: Math.max(intensity / 5, 0.001),
+						u_direction: [1, 0],
+					};
+				},
+			},
+			{
+				fragmentShader: blurFragmentShader,
+				uniforms: ({ effectParams }) => {
+					const intensity =
+						typeof effectParams.intensity === "number"
+							? effectParams.intensity
+							: Number.parseFloat(String(effectParams.intensity));
+					return {
+						u_sigma: Math.max(intensity / 5, 0.001),
+						u_direction: [0, 1],
+					};
+				},
+			},
+		],
+	},
+};