feat(11-04): add UpdateProfileAsync to ProfileService and ImportLogoFromBytesAsync to BrandingService

- ProfileService.UpdateProfileAsync: replaces profile by name and persists the change
- IBrandingService: add ImportLogoFromBytesAsync to interface contract
- BrandingService.ImportLogoFromBytesAsync: validates magic bytes, compresses if > 512KB, returns LogoData
- BrandingService.ImportLogoAsync: refactored to delegate to ImportLogoFromBytesAsync
- ProfileServiceTests: 2 new tests (UpdateProfileAsync happy path + KeyNotFoundException)
- BrandingServiceTests: 2 new tests (ImportLogoFromBytesAsync valid PNG + invalid bytes)
- Tests.csproj: suppress NU1701 for pre-existing LiveCharts2/OpenTK transitive warnings

SharepointToolbox/Services/ProfileService.cs

@@ -51,4 +51,13 @@ public class ProfileService
         profiles.Remove(target);
         await _repository.SaveAsync(profiles);
     }
+
+    public async Task UpdateProfileAsync(TenantProfile profile)
+    {
+        var profiles = (await _repository.LoadAsync()).ToList();
+        var idx = profiles.FindIndex(p => p.Name == profile.Name);
+        if (idx < 0) throw new KeyNotFoundException($"Profile '{profile.Name}' not found.");
+        profiles[idx] = profile;
+        await _repository.SaveAsync(profiles);
+    }
 }