fix(ui): 多项 UI 修复 — 弹窗遮挡/按钮可见性/暗黑闪烁/云函数版本

- 计划编辑弹窗移出 .container 避免 fixed 降级 + 修复滚动
- dock bottom 40rpx→8rpx 紧贴底部, sheet padding 同步调整
- 计划编辑器取消/恢复默认按钮可见性修复(bg 匹配容器)
- ui-btn--danger 按钮可见性修复
- 清除确认弹窗跟随暗黑模式切换
- icons.js build() 中 Fill 路径覆盖 outlined 路径修复
- plan.js getPlanDay 忽略 customPlans 修复
- darkMode.js 冗余三元简化
- util.js fileToDataURI fallback 可读性提升
- theme.js: BASE_VARS 与 getThemeStyle 统一来源, 去 50ms navbar 延迟
- app.wxss: 移除 page transition 和 background-color 减少闪白
- 云函数 wx-server-sdk 版本统一 ~2.6.3, tts cloud.init 一致化
- 闪白问题: wx.setBackgroundColor 三层防护(onLaunch/applyThemeToPage/switchTab)

Co-Authored-By: Claude <noreply@anthropic.com>

utils/icons.js

@@ -118,10 +118,12 @@ const build = (theme) => {
   const out = {}
   Object.keys(PATHS).forEach((name) => {
     if (name.endsWith('Fill')) {
-      const base = name.slice(0, -4)
-      out[base] = _svg(PATHS[name], INACTIVE)
+      // Fill variant: filled path + primary color.
+      // Do NOT write out[base] here — that would overwrite the outlined
+      // variant set by the base-name entry below with the wrong path.
       out[name] = _svg(PATHS[name], p)
     } else {
+      // Outlined variant: outlined path + inactive gray.
       out[name] = _svg(PATHS[name], INACTIVE)
     }
   })