feat: add setup deep link QR support

[faheemKamboh]

Summary

• add qasidrelay://setup deep-link parsing for server URL, phone name, and private relay key
• prefill the Android setup form from scanned setup QR links without enabling messaging automatically
• document setup QR security boundaries and bump Android metadata to 0.1.5

Validation

• local static restricted-permission checks passed
• git diff --check passed
• Android unit/build validation pending GitHub Actions because local Java is unavailable in this session