feat: 深色模式基础设施 (system theme + 跟随系统)

app.js

@@ -1,9 +1,20 @@
 const themeMod = require('./utils/theme')
 const cloud = require('./utils/cloud')
 const storage = require('./utils/storage')
+const darkMod = require('./utils/darkMode')
 
 App({
   async onLaunch() {
+    // Init dark mode listener (refreshes all open pages when system theme changes)
+    darkMod.watchDarkMode((isDark) => {
+      const pages = getCurrentPages()
+      pages.forEach(p => {
+        if (p && typeof p.applyThemeToPage === 'function') {
+          p.applyThemeToPage()
+        }
+      })
+    })
+
     // Init cloud storage (no-op if not configured)
     cloud.init()