feat: node info, build info and acrylic web theme

Squash of recent dev work: return_session login, backend switcher, line
detail timeline, overview strips, node platform/country/ISP info with flags
and icons, build info (version, tag, time) behind site.show_build, and the
acrylic display theme.

packaging/container/Probe.NativeBuild.Containerfile

@@ -1,6 +1,11 @@
 FROM mcr.microsoft.com/dotnet/sdk:10.0-noble-aot AS build
 
 WORKDIR /src/backend
+# 构建信息：CI 通过 --build-arg 传入；不传就是空
+ARG MONITOR_TAG=
+ARG MONITOR_COMMIT=
+ARG MONITOR_BUILT_AT=
+ENV MONITOR_TAG=$MONITOR_TAG MONITOR_COMMIT=$MONITOR_COMMIT MONITOR_BUILT_AT=$MONITOR_BUILT_AT
 COPY restore/backend/ ./
 RUN dotnet restore probe/src/Monitor.Probe -r linux-x64 --artifacts-path /artifacts