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>

pages/settings/settings.js

@@ -1,10 +1,10 @@
 const storage = require('../../utils/storage')
 const themeMod = require('../../utils/theme')
+const darkMod = require('../../utils/darkMode')
 const planMod = require('../../utils/plan')
 const iconsMod = require('../../utils/icons')
 const cloud = require('../../utils/cloud')
 const config = require('../../config')
-const darkMod = require('../../utils/darkMode')
 const util = require('../../utils/util')
 
 /**
@@ -217,7 +217,7 @@ Page({
     this.setData({ currentThemeId: id })
     try {
       const tb = this.getTabBar()
-      if (tb) tb.setData({ themeStyle: themeMod.getThemeStyle(theme) })
+      if (tb) tb.setData({ themeStyle: themeMod.getThemeStyle(theme, darkMod.getInitialDarkMode()) })
     } catch (e) {}
     themeMod.applyThemeToPage(this)
   },