docker: add Dockerfile.runtime / .blogs / .api for ASP.NET images

Three new Dockerfiles, each producing a minimal runtime image
based on mcr.microsoft.com/dotnet/aspnet:10.0:

- Dockerfile.runtime         : Yavsc.Org (port 5000 HTTP)
- Dockerfile.runtime.blogs   : Yavsc.Blogs (port 5004 HTTP)
- Dockerfile.runtime.api     : Yavsc.Api (port 5002 HTTP)

Each one:

1. COPY --from=pazof/yavsc-build-env:debian12-dotnet10-android36-v1
   /app/publish/<project>/ — i.e. the artifacts produced by the
   publish step added in the previous commit.
2. Injects appsettings-org.json via BuildKit secret mount
   (--mount=type=secret,id=yavsc_appsettings). The secret never
   lands in a layer — BuildKit copies it into /app and discards
   the mount.
3. Sets ASPNETCORE_URLS to the project's HTTP port and exposes it.
4. Adds a HEALTHCHECK that pings the root URL.

HTTPS (ports 5001, 5003, 5005) is intentionally NOT exposed in
the Dockerfile: enabling it requires mounting /etc/letsencrypt
(typically via docker-compose) and configuring Kestrel:Certificates
in appsettings-org.json. The compose file in the next commit
documents the volume mount pattern.

Dockerfile.runtime.api

@@ -0,0 +1,33 @@
+# Image runtime pour Yavsc.Api (API REST JSON principale, consommée
+# par les clients headless : PostIt, intégrations tierces, etc.).
+#
+# Cf. Dockerfile.runtime pour le pattern appsettings-org.json via
+# BuildKit secret mount, et le montage optionnel /etc/letsencrypt
+# pour HTTPS en production.
+#
+#   docker build \
+#     --secret id=yavsc_appsettings,src=./appsettings-org.json \
+#     -f Dockerfile.runtime.api \
+#     -t yavsc-api:dev .
+
+# syntax=docker/dockerfile:1.7
+FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS runtime
+
+WORKDIR /app
+
+ARG BUILD_ENV_IMAGE=pazof/yavsc-build-env:debian12-dotnet10-android36-v1
+COPY --from=${BUILD_ENV_IMAGE} /app/publish/Yavsc.Api/ ./
+
+RUN --mount=type=secret,id=yavsc_appsettings,dst=/run/secrets/yavsc_appsettings \
+    cp /run/secrets/yavsc_appsettings /app/appsettings-org.json \
+    && chmod 0644 /app/appsettings-org.json
+
+ENV ASPNETCORE_ENVIRONMENT=Production
+ENV ASPNETCORE_URLS=http://+:5002
+
+EXPOSE 5002
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=20s --retries=3 \
+    CMD wget --quiet --spider http://localhost:5002/ || exit 1
+
+ENTRYPOINT ["dotnet", "Yavsc.Api.dll"]