fix: guard Android user CA trust config

[ZacharyZcR]

Summary

• keep Android network security XML as an exported constant so it can be verified locally
• ensure the generated AndroidManifest explicitly references @xml/network_security_config and keeps cleartext enabled for local/self-hosted deployments
• add a verification script that fails if system or user CA trust anchors are removed from the Android network security config

Refs Termix-SSH/Support#468

Validation

• npm run verify:android-network-security
• npx eslint plugins/withNetworkSecurityConfig.js scripts/verify-android-network-security.cjs
• npx prettier --check plugins/withNetworkSecurityConfig.js scripts/verify-android-network-security.cjs package.json
• npx expo config --type public
• git diff --check
• npx tsc --noEmit (fails on existing app/tabs/settings/KeyboardCustomization.tsx:596 baseline issue)

Note: this PR does not comment on the original Support issue, per maintainer preference.