feat(04-03): add Daten section with Export/Import/Reset buttons in parent area

- HTML section with export-btn, import-btn, reset-btn, hidden file input
- CSS styles for action buttons including danger variant for reset

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/styles/main.css

@@ -803,6 +803,44 @@ h3 {
 	transition: opacity 0.3s ease;
 }
 
+.parent__data-actions {
+	display: flex;
+	flex-direction: column;
+	gap: 0.75rem;
+	max-width: 300px;
+}
+
+.parent__action-btn {
+	font-family: "Quicksand", sans-serif;
+	font-size: 1rem;
+	padding: 0.6rem 1.2rem;
+	border: 2px solid var(--accent-green);
+	background: var(--bg-cream);
+	color: var(--text-dark);
+	border-radius: 8px;
+	cursor: pointer;
+	transition: background 0.2s;
+}
+
+.parent__action-btn:hover {
+	background: var(--bg-forest);
+}
+
+.parent__action-btn--danger {
+	border-color: #d46a6a;
+	color: #d46a6a;
+}
+
+.parent__action-btn--danger:hover {
+	background: #fde8e8;
+}
+
+.parent__data-info {
+	font-size: 0.9rem;
+	color: var(--accent-green);
+	margin-top: 0.5rem;
+}
+
 /* Keyboard */
 .keyboard {
 	display: flex;