feat: re-enable tests in production CI workflow (#217)

Re-add the test-exunit job that runs all ExUnit tests before deployment.
The build-and-deploy job now depends on tests passing first.

All 8837 tests are currently passing locally with 0 failures.

Reviewed-on: graham/towerops-web#217

.forgejo/workflows/production.yaml

@@ -10,9 +10,79 @@ env:
   IMAGE_NAME: graham/towerops-web
 
 jobs:
+  test-exunit:
+    name: Run ExUnit Tests
+    runs-on: ubuntu-22.04
+    env:
+      MIX_ENV: test
+      DATABASE_URL: ecto://postgres:postgres@postgres/towerops_test
+
+    services:
+      postgres:
+        image: timescale/timescaledb:latest-pg17
+        env:
+          POSTGRES_USER: postgres
+          POSTGRES_PASSWORD: postgres
+          POSTGRES_DB: towerops_test
+        options: >-
+          --health-cmd pg_isready
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+
+    steps:
+      - name: Checkout code
+        uses: https://github.com/actions/checkout@v4
+
+      - name: Set up Elixir
+        uses: https://github.com/erlef/setup-beam@v1
+        with:
+          version-type: strict
+          elixir-version: '1.18.1'
+          otp-version: '27.2'
+
+      - name: Cache Mix
+        uses: https://github.com/actions/cache@v4
+        with:
+          path: ~/.mix
+          key: ${{ runner.os }}-mix-1.18.1-27.2
+          restore-keys: ${{ runner.os }}-mix-
+
+      - name: Cache deps
+        uses: https://github.com/actions/cache@v4
+        with:
+          path: deps
+          key: ${{ runner.os }}-deps-${{ hashFiles('mix.lock') }}
+          restore-keys: ${{ runner.os }}-deps-
+
+      - name: Cache _build
+        uses: https://github.com/actions/cache@v4
+        with:
+          path: _build
+          key: ${{ runner.os }}-build-v2-${{ hashFiles('lib/**/*.ex') }}-${{ hashFiles('mix.lock') }}
+          restore-keys: ${{ runner.os }}-build-v2-
+
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libssl-dev libsnmp-dev snmp-mibs-downloader postgresql-client
+
+      - name: Install dependencies
+        run: mix deps.get
+
+      - name: Compile C NIF
+        run: make -C c_src
+
+      - name: Compile (warnings as errors)
+        run: mix compile --warnings-as-errors
+
+      - name: Run tests
+        run: mix test
+
   build-and-deploy:
     name: Build and Deploy to Production
     runs-on: ubuntu-22.04
+    needs: [test-exunit]
 
     steps:
       - name: Checkout code