Bump SixLabors.ImageSharp from 3.1.12 to 4.0.0

---
updated-dependencies:
- dependency-name: SixLabors.ImageSharp
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Directory.Packages.props

@@ -77,7 +77,7 @@
     <PackageVersion Include="Serilog.Sinks.MSSqlServer" Version="9.0.3" />
     <PackageVersion Include="Serilog.Sinks.PeriodicBatching" Version="5.0.0" />
     <PackageVersion Include="Shouldly" Version="4.2.1" />
-    <PackageVersion Include="SixLabors.ImageSharp" Version="3.1.12" />
+    <PackageVersion Include="SixLabors.ImageSharp" Version="4.0.0" />
     <PackageVersion Include="SQLite" Version="3.13.0" />
     <PackageVersion Include="Stripe.net" Version="51.1.0" />
     <PackageVersion Include="Swashbuckle.AspNetCore" Version="10.1.7" />