Add Gitea smoke runner workflow

.gitea/workflows/smoke.yml

@@ -0,0 +1,48 @@
+name: smoke
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  smoke:
+    runs-on:
+      - debian-13
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Verify runner prerequisites
+        run: |
+          set -euo pipefail
+          command -v bash >/dev/null
+          command -v curl >/dev/null
+          command -v gcc >/dev/null
+          command -v pkg-config >/dev/null
+          pkg-config --exists libnftables
+
+      - name: Install .NET SDK
+        run: |
+          set -euo pipefail
+          curl -fsSL https://dot.net/v1/dotnet-install.sh -o dotnet-install.sh
+          bash dotnet-install.sh --channel 10.0 --quality ga --install-dir "$HOME/.dotnet"
+
+      - name: Show .NET info
+        run: |
+          set -euo pipefail
+          "$HOME/.dotnet/dotnet" --info
+
+      - name: Restore
+        run: |
+          set -euo pipefail
+          "$HOME/.dotnet/dotnet" restore
+
+      - name: Build
+        run: |
+          set -euo pipefail
+          "$HOME/.dotnet/dotnet" build --no-restore
+
+      - name: Test
+        run: |
+          set -euo pipefail
+          "$HOME/.dotnet/dotnet" test LibNftables.slnx --no-build