Initial project setup: Next.js frontend + .NET 9 backend

- Frontend: Next.js 16 + shadcn/ui + Tailwind CSS 4
- Backend: .NET 9 Web API with Npgsql health check
- Docker Compose for prod and dev environments
- Woodpecker CI pipeline for auto-deploy
- Health check endpoints for E2E testing

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/Dockerfile

@@ -0,0 +1,13 @@
+FROM mcr.microsoft.com/dotnet/sdk:9.0 AS build
+WORKDIR /src
+COPY src/GBSite.Api/*.csproj ./src/GBSite.Api/
+RUN dotnet restore src/GBSite.Api/GBSite.Api.csproj
+COPY . .
+RUN dotnet publish src/GBSite.Api/GBSite.Api.csproj -c Release -o /app
+
+FROM mcr.microsoft.com/dotnet/aspnet:9.0
+WORKDIR /app
+COPY --from=build /app .
+EXPOSE 5000
+ENV ASPNETCORE_URLS=http://+:5000
+ENTRYPOINT ["dotnet", "GBSite.Api.dll"]