fix(ci): add libsodium-dev to test workflow dependencies

The test.yml workflow's rust-fmt-check, rust-clippy, and rust-tests
jobs were missing libsodium-dev package installation. With the new
use-pkg-config feature enabled, pkg-config must be able to find
libsodium system libraries.

This resolves "libsodium not found via pkg-config" failures in the
test pipeline.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.gitea/workflows/test.yml

@@ -45,6 +45,7 @@ jobs:
             libayatana-appindicator3-dev \
             librsvg2-dev \
             libdbus-1-dev \
+            libsodium-dev \
             pkg-config
       - name: Install Rust components
         run: rustup component add rustfmt
@@ -96,6 +97,7 @@ jobs:
             libayatana-appindicator3-dev \
             librsvg2-dev \
             libdbus-1-dev \
+            libsodium-dev \
             pkg-config
       - name: Install clippy
         run: rustup component add clippy
@@ -133,6 +135,7 @@ jobs:
             libayatana-appindicator3-dev \
             librsvg2-dev \
             libdbus-1-dev \
+            libsodium-dev \
             pkg-config
       - run: cargo test --manifest-path src-tauri/Cargo.toml -- --test-threads=1