[client] Copy trustedproxy package into Docker build context (#6851)

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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Updated the build process to include trusted proxy configuration in
the application image.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

proxy/Dockerfile.multistage

@@ -14,6 +14,7 @@ COPY proxy ./proxy
 COPY route ./route
 COPY shared ./shared
 COPY sharedsock ./sharedsock
+COPY trustedproxy ./trustedproxy
 COPY upload-server ./upload-server
 COPY util ./util
 COPY version ./version