Add raven animation feature with SVG assets and Three.js integration

- Introduced a new SVG asset for the raven silhouette.
- Updated CSS to position and style the raven animation layer.
- Implemented `RavenBurstCanvas` and `RavenFlock` components for rendering animated ravens using Three.js.
- Enhanced `GateTransitProvider` to manage raven animation state and integrate with existing transition logic.
- Added `ravenFx` type and default values for controlling raven animation properties.
- Adjusted transform origins and z-index for improved visual alignment during transitions.

src/index.css

@@ -564,7 +564,7 @@ html.gate-transit-lock body {
   position: absolute;
   inset: 0;
   perspective: 1400px;
-  perspective-origin: 50% 46%;
+  perspective-origin: 50% 50%;
 }
 
 .gate-transit__hero {
@@ -582,8 +582,21 @@ html.gate-transit-lock body {
   user-select: none;
   object-fit: contain;
   filter: drop-shadow(0 10px 32px rgba(0, 0, 0, 0.6));
+  z-index: 1;
 }
 
+.gate-transit__ravens {
+  position: absolute;
+  inset: 0;
+  z-index: 2;
+  pointer-events: none;
+}
+
+.gate-transit__ravens canvas {
+  display: block;
+  width: 100% !important;
+  height: 100% !important;
+}
 
 .gate-transit__veil {
   position: absolute;