feat: expand appearance with shader effects and new style presets

Add 5 WebGL shader background effects (Aurora, Plasma, Digital Rain,
Starfield, Warp Tunnel) via a new bg-shaders.ts engine that shares
a dedicated canvas. Add 5 style presets (Sakura, Ocean, Copper, Vapor,
Monolith) with distinctive font pairings. Remove CSS particles effect
in favor of shader-based alternatives. Fix dot grid visibility and
tune all shader intensities for subtle ambient appearance.

server/src/wled_controller/static/css/base.css

@@ -132,7 +132,8 @@ html.modal-open {
 }
 
 /* ── Ambient animated background ── */
-#bg-anim-canvas {
+#bg-anim-canvas,
+#bg-effect-canvas {
     display: none;
     position: fixed;
     inset: 0;