fix: declare proxy ARGs in build stage so dotnet restore reaches nuget.org

nuget.org is only reachable through the 7890 proxy from the build network
(direct hits return a 302 redirect loop; proxied requests return 200,
verified 8/8). The pipeline passes --build-arg HTTP_PROXY/HTTPS_PROXY, but
Dockerfile did not declare these ARGs in the build stage, so buildkit did
not inject them into the RUN environment and 'dotnet restore' tried nuget.org
directly -> NU1301 'Unable to load the service index'.

Declare HTTP_PROXY/HTTPS_PROXY/NO_PROXY (upper+lower case) as build-stage
ARGs and promote them to ENV so dotnet's HttpClient uses the proxy. Also add
two restore retries (--disable-parallel) to smooth over transient proxy
blips.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/LiveRecorder.WebApi/Dockerfile

@@ -4,6 +4,22 @@ ARG DOTNET_RUNTIME_IMAGE=mcr.microsoft.com/dotnet/aspnet:8.0-bookworm-slim
 FROM ${DOTNET_SDK_IMAGE} AS build
 WORKDIR /src
 
+# Proxy settings for NuGet restore (nuget.org is only reachable via the proxy
+# from the build network). Declared as ARG then promoted to ENV so dotnet and
+# the underlying HttpClient pick them up during restore/publish.
+ARG HTTP_PROXY
+ARG HTTPS_PROXY
+ARG NO_PROXY
+ARG http_proxy
+ARG https_proxy
+ARG no_proxy
+ENV HTTP_PROXY=${HTTP_PROXY} \
+    HTTPS_PROXY=${HTTPS_PROXY} \
+    NO_PROXY=${NO_PROXY} \
+    http_proxy=${http_proxy} \
+    https_proxy=${https_proxy} \
+    no_proxy=${no_proxy}
+
 COPY . .
 
 # Workaround for QEMU ARM64 emulation
@@ -11,7 +27,9 @@ ENV DOTNET_EnableWriteXorExecute=0
 ENV DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=1
 ENV DOTNET_GCConserveMemory=9
 
-RUN dotnet restore "src/LiveRecorder.WebApi/LiveRecorder.WebApi.csproj" -p:RestoreUseStaticGraphEvaluation=true
+RUN dotnet restore "src/LiveRecorder.WebApi/LiveRecorder.WebApi.csproj" -p:RestoreUseStaticGraphEvaluation=true --disable-parallel || \
+    dotnet restore "src/LiveRecorder.WebApi/LiveRecorder.WebApi.csproj" -p:RestoreUseStaticGraphEvaluation=true --disable-parallel || \
+    dotnet restore "src/LiveRecorder.WebApi/LiveRecorder.WebApi.csproj" -p:RestoreUseStaticGraphEvaluation=true --disable-parallel
 RUN dotnet publish "src/LiveRecorder.WebApi/LiveRecorder.WebApi.csproj" -c Release -o /app/publish /p:UseAppHost=false /p:DebugType=None /p:DebugSymbols=false /maxcpucount:1
 
 FROM ${DOTNET_RUNTIME_IMAGE} AS runtime