Revert "Temporarily switch off other workflows than Haskell CI"

This reverts commit 016598f.

Author: andreasabel

.github/workflows/dependabot-auto-approve.yml

@@ -0,0 +1,22 @@
+# https://docs.github.com/en/code-security/dependabot/working-with-dependabot/automating-dependabot-with-github-actions#approve-a-pull-request
+name: Dependabot auto-approve
+on: pull_request
+
+permissions:
+  pull-requests: write
+
+jobs:
+  dependabot:
+    runs-on: ubuntu-latest
+    if: github.actor == 'dependabot[bot]'
+    steps:
+      - name: Dependabot metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v2
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+      - name: Approve a PR
+        run: gh pr review --approve "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GH_TOKEN: ${{secrets.GITHUB_TOKEN}}

.github/workflows/nix-flake.yml

@@ -0,0 +1,42 @@
+name: "Test Nix Flake"
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+jobs:
+  nix:
+    strategy:
+      fail-fast: true
+      matrix:
+        os:
+        - ubuntu-latest
+        - ubuntu-24.04-arm
+        - macos-latest
+    name: Nix on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@v4
+    - uses: cachix/install-nix-action@v31
+      with:
+        extra_nix_config: |
+          trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= hackage-server.cachix.org-1:iw0iRh6+gsFIrxROFaAt5gKNgIHejKjIfyRdbpPYevY=
+          substituters = https://cache.nixos.org/ https://hackage-server.cachix.org/
+    - uses: cachix/cachix-action@v16
+      with:
+        # https://nix.dev/tutorials/continuous-integration-github-actions#setting-up-github-actions
+        name: hackage-server
+        authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+
+    - name: "Check `nix develop` shell"
+      run: nix develop --check
+
+    - name: "Check `nix develop` shell can run command"
+      run: nix develop --command "echo"
+
+    - run: nix build
+
+    - continue-on-error: false
+      run: nix flake check

.github/workflows/update-flake-lock.yml

@@ -0,0 +1,22 @@
+# https://github.com/DeterminateSystems/update-flake-lock
+name: update-flake-lock
+on:
+  workflow_dispatch: # allows manual triggering
+  schedule:
+    - cron: '0 0 1 * *' # runs on first day of the month
+
+jobs:
+  lockfile:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@main
+      - name: Update flake.lock
+        uses: DeterminateSystems/update-flake-lock@main
+        with:
+          pr-title: "Update flake.lock" # Title of PR to be created
+          pr-labels: |                  # Labels to be set on the PR
+            dependencies
+            automated