Epic: Replace Python Edge Proxy with Rust Implementation

The goal of this epic is:

1. All new Edge Proxy deployments use the Rust implementation, not the python implementation
2. The migration from the python Edge Proxy to the Rust implementation is documented and well-tested

The expected approach here will be to publish a new major version of the current `flagsmith/edge-proxy` image with documented upgrade steps (if required) in the release notes.

Start with the current flagsmith/edge-proxy image and compare the Python and Rust implementations, then identify the deployment and release-note entry points involved in publishing a new major version. Done means new Edge Proxy deployments use Rust, migration and any upgrade steps are documented in the release notes, and the migration is well-tested.

Written by the indexing model from the issue text.