• Fix v1.9.13 regression — کاربران v1.9.10 → v1.9.13 upgrade می‌کردن و حس می‌کردن کندتره ([#773](https://github.com/therealaleph/MasterHttpRelayVPN-RUST/issues/773)). علت: `block_doh` در Rust با `#[serde(default)]` برای فیلد `bool` به `false` resolve می‌شد (default trait از Rust)، نه `true` که PR [#763](https://github.com/therealaleph/MasterHttpRelayVPN-RUST/pull/763) قصد داشت. کاربران existing با config.json بدون فیلد `block_doh` و `tunnel_doh = true` (default جدید از #468)، هر DNS lookup رو از مسیر Apps Script می‌فرستادن — ~۱.۵ ثانیه overhead هر page load. حالا `block_doh` با named-default function به `true` resolve می‌شه — مرورگر DoH reject می‌شه + system DNS via tun2proxy فوراً پاسخ می‌ده + هیچ tunnel round-trip دیگه. کاربران power که عمداً DoH از تونل می‌خوان، می‌تونن `block_doh: false` صریح بگذارن. تست: 180 lib + 35 tunnel-node + UI release-mode build همه green. --- • Fix v1.9.13 perceived-slowness regression on upgrade ([#773](https://github.com/therealaleph/MasterHttpRelayVPN-RUST/issues/773)): `block_doh` was using `#[serde(default)]` on a `bool`, which resolves to Rust's `Default::default() = false` rather than the `true` PR [#763](https://github.com/therealaleph/MasterHttpRelayVPN-RUST/pull/763) intended. Existing configs upgrading from v1.9.10 had no `block_doh` field, so they got `false` paired with `tunnel_doh = true` (the new default from #468) — every browser DoH lookup got tunneled through Apps Script, adding ~1.5s overhead per page load. Now `block_doh` uses a named-default function that returns `true` — DoH is rejected at the SOCKS5 listener so the browser falls back to system DNS (instant, via tun2proxy's virtual DNS) and no tunnel round-trip happens. Power users who specifically want DoH-through-tunnel can opt back in with `block_doh: false`. Tests: 180 lib + 35 tunnel-node + UI release-mode build all green.