context-mesh: update client installation page

Update `app/konnect-platform/context-mesh/client-installation.md` with the following info:

- [ ] Transform `http://localhost/mcp/SERVER_PATH` into a variable => add a section on constructing the endpoint from the data plane host plus the /mcp/ path.
- [ ] Explain where to find the server endpoint in the Konnect UI
- [ ] Address MCP Auth (Nothing addresses whether the Context Mesh endpoint on a Konnect data plane requires its own credential. confirm with engineering: if it's unauthenticated by default, the page should say so outright, because readers will assume the opposite and go looking).
- [ ] Add a Windsurf svg to `app/_landing_pages/context-mesh.yaml`