security: restrict network to system CAs, tighten WebView capabilities; v1.9

- AndroidManifest: add networkSecurityConfig to explicitly trust only system
  CAs, preventing user-installed CA cert MITM attacks on claude.ai sessions
- LoginActivity: set javaScriptCanOpenWindowsAutomatically=false (not needed
  for claude.ai login) and databaseEnabled=false (deprecated WebSQL)
- build.gradle.kts: enable buildConfig generation (required for
  BuildConfig.DEBUG guards already used in UsageRepository)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/src/main/AndroidManifest.xml

@@ -11,6 +11,7 @@
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/Theme.ClaudeUsage"
+        android:networkSecurityConfig="@xml/network_security_config"
         android:usesCleartextTraffic="false">
 
         <activity