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/theme.js

@@ -41,10 +41,12 @@ const THEMES = [
   }
 ]
 
-const BASE_VARS = '--text:#333;--text-secondary:#999;--bg:#F5F5F5;--card-bg:#FFFFFF;--border:#EEE;--success:#4CAF50;--success-rgb:76,175,80;--danger:#E53935;--danger-rgb:229,57,53;--primary:#FF6B35;--primary-light:#FF8C5A;--primary-bg:#FFF3ED;--primary-rgb:255,107,53;'
+// Light-mode base CSS custom properties shared between the cold-start export
+// (used by every page as initial data) and getThemeStyle(isDark=false).
+// Update here ONLY — getThemeStyle picks it up for the light branch.
+const BASE_VARS = '--text:#333333;--text-secondary:#999999;--bg:#F5F5F5;--bg-gradient-start:#F5F5F5;--bg-gradient-end:#FAFAFA;--card-bg:#FFFFFF;--bg-soft:#F0F0F0;--border:#EEEEEE;--success:#4CAF50;--success-rgb:76,175,80;--danger:#E53935;--danger-rgb:229,57,53;'
 const DEFAULT_THEME_ID = 'orange'
 const THEME_KEY = 'app_theme'
-let _navColorTimer = null
 
 const getThemeById = (id) => THEMES.find(t => t.id === id) || THEMES[0]
 
@@ -61,15 +63,12 @@ const getCurrentTheme = () => {
 }
 
 const _setNavBarColor = (primary) => {
-  if (_navColorTimer) clearTimeout(_navColorTimer)
-  _navColorTimer = setTimeout(() => {
-    try {
-      wx.setNavigationBarColor({
-        frontColor: '#ffffff',
-        backgroundColor: primary
-      })
-    } catch (e) {}
-  }, 50)
+  try {
+    wx.setNavigationBarColor({
+      frontColor: '#ffffff',
+      backgroundColor: primary
+    })
+  } catch (e) {}
 }
 
 const setTheme = (id) => {
@@ -98,7 +97,7 @@ const getThemeStyle = (theme, isDark = false) => {
   const t = theme || getCurrentTheme()
   const baseVars = isDark
     ? '--text:#E5E5E7;--text-secondary:#98989F;--bg:#2C2C2E;--bg-gradient-start:#2C2C2E;--bg-gradient-end:#38383A;--card-bg:#3A3A3C;--bg-soft:#48484A;--border:#48484A;--success:#30D158;--success-rgb:48,209,88;--danger:#FF6B6B;--danger-rgb:255,107,107;'
-    : '--text:#333333;--text-secondary:#999999;--bg:#F5F5F5;--bg-gradient-start:#F5F5F5;--bg-gradient-end:#FAFAFA;--card-bg:#FFFFFF;--bg-soft:#F0F0F0;--border:#EEEEEE;--success:#4CAF50;--success-rgb:76,175,80;--danger:#E53935;--danger-rgb:229,57,53;'
+    : BASE_VARS
   return `${baseVars}--primary:${t.primary};--primary-light:${t.primaryLight};--primary-bg:${t.primaryBg};--primary-rgb:${t.primaryRgb};`
 }
 
@@ -113,12 +112,29 @@ const applyThemeToPage = (self) => {
   }
   self.setData({ theme, themeStyle: nextStyle, isDark })
   _setNavBarColor(theme.primary)
+
+  // theme.json 的 dark section 只响应系统暗黑模式。用户手动选择暗黑
+  // 但系统是明亮时,窗口背景仍为浅色,切 tab 会闪白。这里用 API 强制设置
+  // 窗口背景,让 tab 切换时的瞬间底色与当前模式一致。
+  const bg = isDark ? '#0F0F12' : '#F5F5F5'
+  try { wx.setBackgroundColor({ backgroundColor: bg, backgroundColorTop: bg, backgroundColorBottom: bg }) } catch (e) {}
+}
+
+/** 仅设置窗口背景色,不触发页面 setData — 供 app.js 冷启动使用 */
+const applyWindowBg = () => {
+  try {
+    const darkMod = require('./darkMode')
+    const isDark = darkMod.getInitialDarkMode()
+    const bg = isDark ? '#0F0F12' : '#F5F5F5'
+    wx.setBackgroundColor({ backgroundColor: bg, backgroundColorTop: bg, backgroundColorBottom: bg })
+  } catch (e) {}
 }
 
 module.exports = {
   THEMES,
   DEFAULT_THEME_ID,
   BASE_VARS,
+  applyWindowBg,
   getThemeById,
   getCurrentTheme,
   setTheme,