feat(dns): add intelligent DNS Benchmark, Auto-Tuner & clean defaults
- Implement ucode module dns/benchmark.uc:
* Probes major DNS servers (Yandex, Cloudflare, Google, Quad9, AdGuard, Comss, Mullvad, Control D) across UDP 53 and DoH.
* Measures latency, packet loss, and detects ISP DNS poisoning/hijacking.
* Intelligent recommendation engine computes optimal primary DNS (prefers encrypted DoH if fast), bootstrap plain UDP, fallback plain UDP from independent provider, and upstream mode (sequential/parallel).
* Supports CLI execution (tachyon dns_benchmark, tachyon dns_autotune --apply) and background async worker mode for LuCI UI.
- LuCI Web UI modal (renderDnsBenchmarkModal.ts):
* Real-time progress bar, responsive results table with latency rating badges.
* Recommendation summary card with one-click 'Apply Recommended DNS' action.
* Added '⚡ Auto-Tune & Benchmark DNS' button in Settings -> DNS tab.
- Added comprehensive unit tests in vitest (538/538 passed) and tests/dns_benchmark.sh.
- Added Russian PO translations.
Dushnilin
84658d84dc