Replaces the backend-test MariaDB service with an explicit docker run

The services: block was silently broken on this runner: job and service
containers both use host networking here, so the ports: mapping was
ignored and the mariadb:11 service ended up sharing the host's own port
3306 -- which something else on this runner already answers on (root auth
was rejected with a password nothing but this job ever set). Replaced with
an explicit `docker run` on host port 3307, bypassing that collision, plus
a readiness loop. Also fixes the readiness command itself: mariadb:11 does
not provide a `mysqladmin` alias, the correct binary is `mariadb-admin`
(verified locally against the exact image before pushing this).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FWyStNL2ZsjrS7FLd7xvvN

.gitea/workflows/continuous_integration.yaml

@@ -134,32 +134,48 @@ jobs:
     # other test project here, which mocks/uses EF Core InMemory and never touches a real
     # database. Without a real, reachable MariaDB, those tests fail on the connection itself
     # before any assertion runs.
-    services:
-      mariadb:
-        image: mariadb:11
-        env:
-          MARIADB_ROOT_PASSWORD: ci_test_password
-          MARIADB_DATABASE: SlpModularCms
-        ports:
-          - 3306:3306
-        options: >-
-          --health-cmd="mysqladmin ping --silent"
-          --health-interval=10s
-          --health-timeout=5s
-          --health-retries=5
+    #
+    # A `services:` block was tried first and rejected: this runner uses host networking for
+    # job AND service containers ("--network and --net in the options will be ignored" in the
+    # job log), so the `ports:` mapping was silently ignored, and the mariadb:11 service ended
+    # up sharing the host's network namespace directly on port 3306 -- which something else on
+    # this runner already answers on (root auth was rejected by a server that was clearly NOT
+    # the freshly-initialized container: "Access denied ... using password: YES" against a
+    # password nothing but this job ever set). An explicitly `docker run` container below,
+    # published on host port 3307 instead of 3306, avoids that collision entirely.
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-dotnet@v4
         with:
           dotnet-version: ${{ env.DOTNET_VERSION }}
+      - name: Start MariaDB for SlpModularCms.Api.Tests
+        run: |
+          docker run -d --name ci-mariadb \
+            -e MARIADB_ROOT_PASSWORD=ci_test_password \
+            -e MARIADB_DATABASE=SlpModularCms \
+            -p 3307:3306 \
+            mariadb:11
+          for i in $(seq 1 30); do
+            # mariadb:11 does not provide a `mysqladmin` alias -- verified locally against this
+            # exact image; the correct binary here is `mariadb-admin`.
+            if docker exec ci-mariadb mariadb-admin ping -uroot -pci_test_password --silent 2>/dev/null; then
+              echo "MariaDB is ready."
+              break
+            fi
+            echo "Waiting for MariaDB... ($i/30)"
+            sleep 2
+          done
       - name: Test (Release)
         env:
           # Overrides the placeholder in SlpModularCms.Api/appsettings.Development.json for this
           # CI run only -- ASP.NET Core's configuration layering applies environment variables
           # after appsettings.*.json, so this reaches SlpModularCms.Api.Tests' WebApplicationFactory
-          # without touching any committed appsettings file.
-          ConnectionStrings__DefaultConnection: "Server=127.0.0.1;Port=3306;Database=SlpModularCms;Uid=root;Pwd=ci_test_password"
+          # without touching any committed appsettings file. Port 3307, not 3306 -- see above.
+          ConnectionStrings__DefaultConnection: "Server=127.0.0.1;Port=3307;Database=SlpModularCms;Uid=root;Pwd=ci_test_password"
         run: dotnet test SlpModularCms.sln -c Release
+      - name: Stop MariaDB for SlpModularCms.Api.Tests
+        if: always()
+        run: docker rm -f ci-mariadb || true
 
   # --- Gate 3: vulnerability scan ---
   # `dotnet list package --vulnerable` always exits 0, even when it reports vulnerabilities, so the