tauri-plugin-stronghold pulls in libsodium-sys-stable which panics at
build time if libsodium is not found via pkg-config — it does not compile
from source. All builder images and the test job inline apt installs were
missing libsodium-dev, breaking every Rust compilation step.
- Add libsodium-dev to Dockerfile.linux-amd64
- Add libsodium-dev (host) + libsodium-dev:arm64 (cross target) to
Dockerfile.linux-arm64
- Add libsodium-dev to all three Rust jobs in test.yml
- Add inline apt-get install to linux-amd64 and linux-arm64 Build steps
in auto-tag.yml and release-beta.yml (bridges the timing race between
build-images and auto-tag triggering on the same push)
- Add SODIUM_LIB_DIR + SODIUM_STATIC to Windows Build env (Dockerfile
already pre-builds libsodium; this tells the crate where to find it)
