chore: move the server, services and tools to .NET 10

.NET 8 and 9 reach end of support on 2026-11-10; .NET 10 is the LTS release
(supported until November 2028).

- net9.0 -> net10.0 for every server, service, gateway, test and tool project
- ASP.NET Core / EF Core / SignalR Redis 10.0.13, Npgsql EF 10.0.3,
  Serilog.AspNetCore 10.0.0
- Dockerfile / Dockerfile.service: sdk and aspnet 10.0 images
- release workflow: setup-dotnet 10.0.x
- Jenkins build agent: dotnet-sdk-10.0 (was 8.0); the ClientMod still
  targets net6.0, which MelonLoader loads
- README / architecture docs, .gitignore data paths

DorkNet.AdminMobile (MAUI) stays on net9.0 for now: building it needs the
Android/iOS workloads.

ci/jenkins/Dockerfile

@@ -28,7 +28,7 @@ RUN apt-get update \
  && wget -q "https://packages.microsoft.com/config/debian/${VERSION_ID}/packages-microsoft-prod.deb" -O /tmp/ms.deb \
  && dpkg -i /tmp/ms.deb && rm /tmp/ms.deb \
  && apt-get update \
- && apt-get install -y --no-install-recommends dotnet-sdk-8.0 \
+ && apt-get install -y --no-install-recommends dotnet-sdk-10.0 \
  && rm -rf /var/lib/apt/lists/*
 
 # ---- Python with LIEF (DT_NEEDED injection into libmain.so) ---------------