chore: bump versions to 1.7.9 (Cargo + Android)

Patch release for the Win7 i686 binary fix shipped via #323.
No code changes; CI workflow change only — Cargo, Gradle, and
changelog bumps in lockstep so the release produces a fresh
i686 Windows binary built against Rust 1.77.2.

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

android/app/build.gradle.kts

@@ -14,8 +14,8 @@ android {
         applicationId = "com.therealaleph.mhrv"
         minSdk = 24 // Android 7.0 — covers 99%+ of live devices.
         targetSdk = 34
-        versionCode = 153
-        versionName = "1.7.8"
+        versionCode = 154
+        versionName = "1.7.9"
 
         // Ship all four mainstream Android ABIs:
         //   - arm64-v8a      — 95%+ of real-world Android phones since 2019