Extract a shared Logo component for the header and footer

The header inlined its own logo/wordmark fallback markup. Pull it into
components/logo.tsx so the footer can show the same mark, and drop the
now-unneeded 'use client' from the root layout.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VUttSNLkLPvvR6Xf75QA1K

app/layout.tsx

@@ -1,5 +1,3 @@
-'use client';
-
 import React from 'react';
 import './globals.css';
 import { Geist, Geist_Mono } from 'next/font/google';