feat: refactor to FastAPI architecture v2.0

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/static/js/export.js

@@ -0,0 +1,34 @@
+/**
+ * JSON import/export for Scenar Creator.
+ */
+
+function exportJson() {
+    if (!window.currentDocument) {
+        showStatus('No document to export', 'error');
+        return;
+    }
+    const json = JSON.stringify(window.currentDocument, null, 2);
+    const blob = new Blob([json], { type: 'application/json' });
+    API.downloadBlob(blob, 'scenar_export.json');
+}
+
+function handleJsonImport(event) {
+    const file = event.target.files[0];
+    if (!file) return;
+
+    const reader = new FileReader();
+    reader.onload = function (e) {
+        try {
+            const doc = JSON.parse(e.target.result);
+            if (!doc.event || !doc.blocks || !doc.program_types) {
+                throw new Error('Invalid ScenarioDocument format');
+            }
+            window.currentDocument = doc;
+            showImportedDocument(doc);
+            showStatus('JSON imported successfully', 'success');
+        } catch (err) {
+            showStatus('JSON import error: ' + err.message, 'error');
+        }
+    };
+    reader.readAsText(file);
+}