feat: Add Nanaxe server with Docker, GitHub Actions CI/CD, and auto-deployment

- Add complete server infrastructure with Gitea, API, PostgreSQL
- Implement Obsidian-compatible markdown mindmap converter
- Add Flutter service for server synchronization
- Configure GitHub Actions for automated build and deploy
- Add production docker-compose with health checks
- Include VPS setup and deployment scripts
- Add comprehensive deployment documentation

lib/models/mind_map_model.dart

@@ -35,8 +35,12 @@ class MindMapNode {
 
   factory MindMapNode.fromFirestore(DocumentSnapshot doc) {
     final data = doc.data() as Map<String, dynamic>;
+    return MindMapNode.fromMap(doc.id, data);
+  }
+
+  factory MindMapNode.fromMap(String id, Map<String, dynamic> data) {
     return MindMapNode(
-      id: doc.id,
+      id: id,
       projectId: data['projectId'] ?? '',
       parentId: data['parentId'],
       level: data['level'] ?? 0,