Merge feature/ci-drift-check (DB-3): CI EF-Migrations-Drift-Check

.gitea/workflows/ci.yml: nach Build zwei Steps (dotnet-ef install + has-pending-model-changes)
→ faengt Snapshot/Migrations-Drift im Runner (EnsureCreated-SQLite-Testhost sieht das nie).
Automatisiert die manuelle MERGE-GATE-Regel. Nur CI-Config, kein Code/Schema.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -48,6 +48,19 @@ jobs:
       - name: Build
         run: dotnet build GerbilManager.slnx --no-restore -c Release
 
+      - name: dotnet-ef Tool installieren
+        run: dotnet tool install --global dotnet-ef --version 10.0.*
+
+      - name: DB-3 EF Migrations Drift-Check
+        # Fails CI if the EF model diverges from the snapshot (i.e. a code change touched
+        # entities/OnModelCreating without generating a matching migration). Catches exactly
+        # the class of drift the SQLite/EnsureCreated test host is blind to.
+        run: >
+          dotnet ef migrations has-pending-model-changes
+          --project GerbilManagerWebAPI
+          --startup-project GerbilManagerWebAPI
+          --no-build -c Release
+
       - name: Tests ausfuehren
         run: dotnet test GerbilManager.slnx --no-build -c Release --logger "console;verbosity=normal"