Rewrite from Go + vanilla JS to Python (FastAPI) + React (TypeScript)

- Backend: Python 3.12 with FastAPI, SQLAlchemy, boto3
- Frontend: React 18 with TypeScript, Vite build tooling
- Updated Dockerfile for multi-stage Node + Python build
- Updated CI pipeline for Python backend
- Removed old Go code (cmd/, internal/, go.mod, go.sum)
- Updated README with new tech stack documentation

frontend/src/components/Layout.tsx

@@ -0,0 +1,37 @@
+import { ReactNode } from 'react';
+import { Link } from 'react-router-dom';
+import './Layout.css';
+
+interface LayoutProps {
+  children: ReactNode;
+}
+
+function Layout({ children }: LayoutProps) {
+  return (
+    <div className="layout">
+      <header className="header">
+        <div className="container header-content">
+          <Link to="/" className="logo">
+            <span className="logo-icon">🌳</span>
+            <span className="logo-text">Orchard</span>
+          </Link>
+          <nav className="nav">
+            <Link to="/">Groves</Link>
+          </nav>
+        </div>
+      </header>
+      <main className="main">
+        <div className="container">
+          {children}
+        </div>
+      </main>
+      <footer className="footer">
+        <div className="container">
+          <p>Orchard - Content-Addressable Storage System</p>
+        </div>
+      </footer>
+    </div>
+  );
+}
+
+export default Layout;