Sing v0.2: multi-page navigation + sing-box engine

- Add 4-tab navigation (Home/Nodes/Logs/Settings) with BottomNavigationView
- Replace tun2socks direct proxy with sing-box engine for multi-protocol support
  (socks5, shadowsocks, vmess, vless)
- Dual-process architecture: sing-box (mixed inbound :10801) + tun2socks (TUN fd bridge)
- Add node management: NodeStore (SharedPreferences), add/delete/select nodes
- Add SingBoxConfig: dynamic sing-box JSON config generation (1.13+ format)
- Add real-time log viewer with incremental reading
- Add settings page (DNS, auto-connect, about)
- Migrate to AppCompatActivity + MaterialComponents theme
- Fix fork_exec.c: guard keepFd=-1 for sing-box (no TUN fd needed)
- Delete unused files: TcpProxy, Socks5Client, ConfigReader, config.jsonc

Tested: VPN connects, exit IP = 156.225.28.220, HTTPS works, all tabs functional.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists