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/locales/zh.json

@@ -1749,15 +1749,24 @@
     "appearance.preset.arctic": "极地",
     "appearance.preset.terminal": "终端",
     "appearance.preset.neon": "霓虹",
+    "appearance.preset.sakura": "樱花",
+    "appearance.preset.ocean": "海洋",
+    "appearance.preset.copper": "铜色",
+    "appearance.preset.vapor": "蒸汽波",
+    "appearance.preset.monolith": "黑白",
     "appearance.preset.applied": "样式已应用",
     "appearance.bg.label": "背景效果",
     "appearance.bg.hint": "在界面后面添加环境背景层。",
     "appearance.bg.none": "无",
     "appearance.bg.noise": "噪声场",
+    "appearance.bg.aurora": "极光",
+    "appearance.bg.plasma": "等离子",
+    "appearance.bg.rain": "数字雨",
+    "appearance.bg.stars": "星空",
+    "appearance.bg.warp": "隧道",
     "appearance.bg.grid": "点阵",
     "appearance.bg.mesh": "渐变网格",
     "appearance.bg.scanlines": "扫描线",
-    "appearance.bg.particles": "粒子",
     "appearance.bg.applied": "背景效果已应用",
 
     "color_strip": {