ci: add check and lint workflows

.gitea/workflows/check.yaml

@@ -0,0 +1,33 @@
+name: Check
+on:
+  push:
+    paths:
+      - '**.nix'
+      - flake.lock
+      - npins/sources.json
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  nix-flake:
+    name: Nix flake
+    runs-on: ubuntu-24.04
+
+    steps:
+      - name: Install QEMU
+        run: |
+          sudo apt update -y
+          sudo apt install -y qemu-user-static
+
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v22
+        with:
+          extra-conf: |
+            log-lines = 500
+            extra-platforms = aarch64-linux
+
+      - name: Clone repository
+        uses: actions/checkout@v6
+
+      - name: Check Nix flake outputs
+        run: nix flake check --all-systems --show-trace

.gitea/workflows/lint.yaml

@@ -0,0 +1,35 @@
+name: Lint
+on:
+  push:
+    paths:
+      - '**.nix'
+      - flake.lock
+      - npins/sources.json
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  nix-expressions:
+    name: Nix expressions
+    runs-on: ubuntu-24.04
+
+    steps:
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v22
+        with:
+          extra-conf: |
+            log-lines = 500
+
+      - name: Clone repository
+        uses: actions/checkout@v6
+
+      - name: Check if properly formatted
+        run: nix fmt -- -c .
+
+      - name: Static code analysis
+        if: always()
+        run: nix run nixpkgs#statix -- check -i npins
+
+      - name: Scan for dead code
+        if: always()
+        run: nix run nixpkgs#deadnix -- -f --exclude npins