docs: Add NuGet Package Management section to CLAUDE.md

- Document Central Package Management (CPM) with Package Source Mapping
- Explain package source configuration (nuget.org vs musk private feed)
- Describe how nuget.config is used across different environments
- Add troubleshooting context for NU1507 warning resolution

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

CLAUDE.md

@@ -141,6 +141,37 @@ When running with docker-compose:
 - Docker & Docker Compose for containerization
 - Drone CI/CD on Kubernetes
 
+## NuGet Package Management
+
+The project uses **Central Package Management (CPM)** with **Package Source Mapping** to manage NuGet dependencies:
+
+### Package Sources
+
+- **nuget.org**: All public packages (Microsoft.*, Serilog.*, etc.)
+- **musk** (private): Internal `Nocr.*` contract packages
+
+### Configuration
+
+The `nuget.config` file in the project root defines package source mapping:
+```xml
+<packageSourceMapping>
+  <packageSource key="musk">
+    <package pattern="Nocr.*" />
+  </packageSource>
+  <packageSource key="nuget.org">
+    <package pattern="*" />
+  </packageSource>
+</packageSourceMapping>
+```
+
+### How It Works
+
+1. **Local Development**: Copy `nuget.config` to each submodule root when needed
+2. **CI/CD**: Drone automatically copies `nuget.config` to `/root/.nuget/NuGet/NuGet.Config`
+3. **Docker Builds**: Kaniko copies `nuget.config` to submodule root before building
+
+This eliminates NuGet warning NU1507 and ensures consistent package resolution across all environments.
+
 ## CI/CD Pipeline
 
 **📖 See [_deploy/README.md](_deploy/README.md) for full CI/CD documentation.**