chore: add Docker deployment setup and health check wiring

- Add multi-stage Dockerfile for backend (SDK build → ASP.NET runtime,
  non-root user, /health HEALTHCHECK)
- Add docker-compose.dev.yml orchestrating extrudex-api + control-center-web
- Add deploy.sh convenience script wrapping docker compose up --build
- Wire ASP.NET health checks: AddHealthChecks().AddNpgSql() + MapHealthChecks("/health")
- Add backend .dockerignore (comprehensive pattern list)
- Exclude frontend/dist, frontend/node_modules, frontend/.angular from git

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

backend/Extrudex.csproj

@@ -9,6 +9,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="AspNetCore.HealthChecks.NpgSql" Version="9.0.0" />
     <PackageReference Include="FluentValidation.DependencyInjectionExtensions" Version="12.1.1" />
     <PackageReference Include="Microsoft.EntityFrameworkCore" Version="9.0.3" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="9.0.3" />