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.

1 files changed, 9 insertions, 3 deletions

diff --git a/apps/web/src/components/editor/panels/timeline/index.tsx b/apps/web/src/components/editor/panels/timeline/index.tsx
index 18f768a9..d89d270d 100644
--- a/apps/web/src/components/editor/panels/timeline/index.tsx
+++ b/apps/web/src/components/editor/panels/timeline/index.tsx
@@ -27,7 +27,7 @@ import type { SnapPoint } from "@/lib/timeline/snap-utils";
 import type { TimelineTrack } from "@/types/timeline";
 import {
 	TIMELINE_CONSTANTS,
-	TRACK_ICONS,
+	TRACK_CONFIG,
 } from "@/constants/timeline-constants";
 import { useElementInteraction } from "@/hooks/timeline/element/use-element-interaction";
 import {
@@ -161,6 +161,7 @@ export function Timeline() {
 		shouldIgnoreClick,
 	} = useSelectionBox({
 		containerRef: tracksContainerRef,
+		headerRef: timelineHeaderRef,
 		onSelectionComplete: (elements) => {
 			setElementSelection({ elements });
 		},
@@ -326,7 +327,7 @@ export function Timeline() {
 						<DragLine
 							dropTarget={dropTarget}
 							tracks={timeline.getTracks()}
-							isVisible={isDragOver}
+							isVisible={isDragOver && !dropTarget?.targetElement}
 							headerHeight={timelineHeaderHeight}
 						/>
 						<DragLine
@@ -453,6 +454,11 @@ export function Timeline() {
 															}}
 															onTrackClick={handleTracksClick}
 															shouldIgnoreClick={shouldIgnoreClick}
+															targetElementId={
+																isDragOver
+																	? dropTarget?.targetElement?.elementId ?? null
+																	: null
+															}
 														/>
 													</div>
 												</ContextMenuTrigger>
@@ -523,7 +529,7 @@ export function Timeline() {
 }
 
 function TrackIcon({ track }: { track: TimelineTrack }) {
-	return <>{TRACK_ICONS[track.type]}</>;
+	return <>{TRACK_CONFIG[track.type].icon}</>;
 }
 
 function TrackToggleIcon({