ci(backend): map postgres service to host:5441 instead of 5432

The self-hosted runner host already has brew postgres@14 listening on
127.0.0.1:5432, so binding the test postgres container to host 5432
produces a port-already-allocated error. Pick 5441 and update the
connection string accordingly.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
           --health-timeout 5s
           --health-retries 5
         ports:
-          - 5432:5432
+          - 5441:5432
     steps:
       - uses: actions/checkout@v4
 
@@ -45,7 +45,7 @@ jobs:
 
       - name: Test
         env:
-          ConnectionStrings__Default: Host=localhost;Port=5432;Database=food_market_test;Username=postgres;Password=postgres
+          ConnectionStrings__Default: Host=localhost;Port=5441;Database=food_market_test;Username=postgres;Password=postgres
         run: dotnet test food-market.sln --no-build -c Release --verbosity normal || echo "No tests yet"
 
   web: