Use session name for chat alignment and send connect request

[noahfraiture]

Motivation

• Chat bubble alignment previously relied on a hardcoded local label ("You") so ownership detection was incorrect when the session name is random.
• The app needs to register the per-session name with the server so remote messages and local messages can be correlated by actual user identity.

Description

• Update App.tsx to generate a per-session guest name with createGuestName() and a session token using crypto.randomUUID() and send a connect request over WebSocket ({ type: "connect", token, name }).
• Change message creation to use the session userName when appending outgoing chat entries and when sending chat requests.
• Update ChatPanel.tsx to accept a new currentUserName prop and compute ownership with message.user.name === currentUserName, choosing alignment classes and bubble tone accordingly while still rendering the local sender label as You for clarity.
• Add a small UX polish showing different footer text (Sent / Delivered) and a brief timestamp placeholder per message.

Testing

• Started the frontend dev server with pnpm --dir frontend dev --host 0.0.0.0 --port 4173, which launched successfully.
• Captured a headless browser screenshot via Playwright against http://127.0.0.1:4173, which completed successfully and produced an artifact image.
• No unit tests were run for these UI changes.

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Codex Task