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/index.css

@@ -0,0 +1,47 @@
+* {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+:root {
+  --primary: #2d5a27;
+  --primary-light: #4a8c3f;
+  --primary-dark: #1e3d1a;
+  --secondary: #8b4513;
+  --background: #f5f5f0;
+  --surface: #ffffff;
+  --text: #333333;
+  --text-light: #666666;
+  --border: #e0e0e0;
+  --success: #28a745;
+  --error: #dc3545;
+  --warning: #ffc107;
+}
+
+body {
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
+  background-color: var(--background);
+  color: var(--text);
+  line-height: 1.6;
+}
+
+a {
+  color: var(--primary);
+  text-decoration: none;
+}
+
+a:hover {
+  text-decoration: underline;
+}
+
+button {
+  cursor: pointer;
+  font-family: inherit;
+}
+
+.container {
+  max-width: 1200px;
+  margin: 0 auto;
+  padding: 0 20px;
+}