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BREAKING app package, database, and URLs are no longer valid

app.config.js

@@ -1,7 +1,7 @@
 const appJson = require('./app.json');
 
 const isDevVariant = process.env.APP_VARIANT === 'dev';
-const releaseApiBaseUrl = 'https://bbs.littlelan.cn/api/v1';
+const releaseApiBaseUrl = 'https://withyou.littlelan.cn/api/v1';
 const releaseUpdatesBaseUrl = 'https://updates.littlelan.cn';
 const devApiBaseUrl = process.env.EXPO_PUBLIC_API_BASE_URL || 'http://192.168.31.238:8080/api/v1';