CI: connect backend tests to PostgreSQL service hostname

.gitea/workflows/ci.yml

@@ -35,10 +35,8 @@ jobs:
           POSTGRES_DB: kartsell
           POSTGRES_USER: kartsell
           POSTGRES_PASSWORD: kartsell
-        # The Gitea runner already uses host port 5432 for its production tunnel.
-        # Keep the service isolated on a dedicated host port for CI.
-        ports: ["15432:5432"]
         options: >-
+          --network-alias postgres
           --health-cmd "pg_isready -U kartsell"
           --health-interval 10s
           --health-timeout 5s
@@ -52,16 +50,16 @@ jobs:
       - run: dotnet build KArtSell.sln --no-restore -c Release
       - run: dotnet run --project src/KArtSell.DbMigrator -c Release --no-build
         env:
-          KARTSELL_POSTGRES: Host=localhost;Port=15432;Database=kartsell;Username=kartsell;Password=kartsell
+          KARTSELL_POSTGRES: Host=postgres;Port=5432;Database=kartsell;Username=kartsell;Password=kartsell
       - run: dotnet run --project src/KArtSell.DbMigrator -c Release --no-build
         env:
-          KARTSELL_POSTGRES: Host=localhost;Port=15432;Database=kartsell;Username=kartsell;Password=kartsell
+          KARTSELL_POSTGRES: Host=postgres;Port=5432;Database=kartsell;Username=kartsell;Password=kartsell
       - name: Run backend tests with hang evidence
         run: >-
           dotnet test KArtSell.sln --no-build -c Release --logger trx
           --blame-hang --blame-hang-timeout 2m
         env:
-          KARTSELL_POSTGRES: Host=localhost;Port=15432;Database=kartsell;Username=kartsell;Password=kartsell
+          KARTSELL_POSTGRES: Host=postgres;Port=5432;Database=kartsell;Username=kartsell;Password=kartsell
 
       - name: Check OpenAPI Breaking Changes (AEG-X-008)
         run: |