Rebrand the entire application from "胡萝卜社区" (Carrot BBS) to "威友" (WithYou), including:

- Update app name, package name (skin.carrot.bbs → cn.qczlit.withyou), and bundle identifier
- Update API endpoints (bbs.littlelan.cn → withyou.littlelan.cn)
- Update URL scheme (carrotbbs:// → withyou://)
- Rename database from carrot_bbs to with_you
- Update CI/CD pipeline image names and artifact naming
- Add Android signing configuration for release builds
- Update all UI text and comments throughout the codebase
- Refactor registerStore to use in-memory state instead of AsyncStorage persistence
- Improve WebRTC track handling and call stream management
- Add metro platform resolution for native platform support

BREAKING app package, database, and URLs are no longer valid

src/app-navigation/AppDesktopShell.tsx

@@ -1,4 +1,4 @@
-import React, { useCallback, useEffect, useMemo, useState } from 'react';
+import React, { useCallback, useEffect, useMemo, useState } from 'react';
 import {
   View,
   StyleSheet,
@@ -187,7 +187,7 @@ export function AppDesktopShell() {
       >
         <View style={styles.sidebarHeader}>
           <MaterialCommunityIcons name="carrot" size={32} color={colors.primary.main} />
-          {!isCollapsed && <Text style={styles.logoText}>胡萝卜BBS</Text>}
+          {!isCollapsed && <Text style={styles.logoText}>威友</Text>}
         </View>
         <ScrollView style={styles.sidebarContent} showsVerticalScrollIndicator={false}>
           {NAV_ITEMS.map((item) => {