fix: replace setup-rust-toolchain action with inline rustup commands

The Swatinem/rust-cache action bundled in actions-rust-lang/setup-rust-toolchain@v1
was updated to require node24, which is not supported by the self-hosted act
runner (v0.2.6). Even with cache:false, act eagerly loads pre-steps for all
nested actions regardless of conditions, and the node24 incompatibility in
the rust-cache pre-step caused the parent step to be marked as failed —
skipping Run tests entirely.

Replace both test and lint toolchain setup steps with direct rustup shell
commands to eliminate the dependency on the composite action entirely.

.gitea/workflows/build-and-deploy.yaml

@@ -20,12 +20,16 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Set up Rust toolchain
-        uses: actions-rust-lang/setup-rust-toolchain@v1
-        with:
-          cache: false
+        run: |
+          rustup update stable
+          rustup default stable
+        env:
+          RUSTFLAGS: -D warnings
 
       - name: Run tests
         run: cargo test --all-targets --all-features
+        env:
+          RUSTFLAGS: -D warnings
 
   lint:
     needs: test
@@ -35,10 +39,10 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Set up Rust toolchain
-        uses: actions-rust-lang/setup-rust-toolchain@v1
-        with:
-          components: rustfmt, clippy
-          cache: false
+        run: |
+          rustup update stable
+          rustup default stable
+          rustup component add rustfmt clippy
 
       - name: Cargo fmt
         run: cargo fmt --all -- --check