Add persistent UI scaling for v0.1.6

[oshtz]

Summary

• add a persistent 80–140% UI scale control with Reset in Settings
• apply scaling through Tauri's native webview zoom capability
• align release metadata for v0.1.6

Verification

• npm run check:version
• npm run audit:prod
• npx tsc --noEmit -p tsconfig.app.json
• npm run lint
• npm test (43 tests)
• npm run build
• npm run smoke:routes (33 tests)
• cargo fmt --all -- --check
• cargo clippy --all-targets -- -D warnings
• cargo test --lib (74 tests)
• cargo audit
• cargo +1.88.0 check --locked
• native Windows Tauri development launch