v1.7.0: native udpgw, Android UI restructure, release tooling

Highlights:
- Native udpgw protocol in Full mode (#222) — Telegram voice/video
  calls and Google Meet now work in Full mode on Android. UDP flows
  through one persistent TCP tunnel (instead of session-per-destination)
  so STUN/RTP flow counts no longer stall. Requires redeploying the
  tunnel-node Docker image (ghcr.io/therealaleph/mhrv-tunnel-node:1.7.0).
- Android home screen restructure (#258, closes #246) — Connect button
  now pinned under Mode field, App picker shows pre-selected apps at
  top. With long deployment-ID lists, Connect no longer scrolls
  off-screen.
- release-drafter + prepare-release tooling (#260) — incrementally
  drafts release notes from merged PR titles; manual workflow_dispatch
  prepares version bumps + changelog stubs.

No protocol breaking changes; existing apps_script-mode and Full-mode
deployments work unchanged. Full-mode users get udpgw automatically
once the tunnel-node Docker image is updated.

Thanks to @yyoyoian-pixel and @dazzling-no-more.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mhrv-rs"
-version = "1.6.5"
+version = "1.7.0"
 edition = "2021"
 description = "Rust port of MasterHttpRelayVPN -- DPI bypass via Google Apps Script relay with domain fronting"
 license = "MIT"