Add rename modal and persistent identity with connect update

[noahfraiture]

Motivation

• Provide a simple, pretty place in the UI for users to rename themselves and persist that identity across sessions.
• Leverage the backend behavior that accepts a new connect request with the same token to update the name for an existing identity.

Description

• Add a daisyUI-styled rename modal and compact avatar to the top bar, exposing a displayName and onRename API (file frontend/src/TopBar.tsx).
• Persist client identity (token + name) in localStorage and expose helpers to load/save identity and create a token (file frontend/src/main.tsx).
• Send a connect request over the WebSocket on load and when the name is changed using the existing useWsRequest helper (file frontend/src/main.tsx).
• Wire the current display name into local message echoes so sent messages reflect the chosen name (file frontend/src/App.tsx).

Testing

• Installed dependencies with pnpm install and the install step completed successfully.
• Started the dev server (vite) and confirmed the app served locally (HTTP 200 response), which succeeded.
• Automated Playwright script opened the app, clicked the Rename button and captured a screenshot of the modal (artifacts/rename-modal.png), which succeeded.
• No unit or CI tests were run as part of this change.

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Codex Task