feat: Add config persistence

- Create ConfigManager for save/load
- Save config to config.json
- Load config on startup
- Persist API key, model, base_url
- Fix config not saved issue

graph_memory_tui/services/config_manager.py

@@ -0,0 +1,46 @@
+"""
+配置管理 - 支持持久化
+"""
+
+import json
+from pathlib import Path
+from .config import AppConfig
+
+
+class ConfigManager:
+    """配置管理器 - 支持持久化"""
+    
+    def __init__(self, config_file: str = "config.json"):
+        self.config_file = Path(config_file)
+    
+    def save(self, config: AppConfig) -> None:
+        """保存配置到文件"""
+        data = {
+            "api_key": config.api_key,
+            "model": config.model,
+            "base_url": config.base_url
+        }
+        
+        with open(self.config_file, 'w', encoding='utf-8') as f:
+            json.dump(data, f, indent=2)
+    
+    def load(self) -> AppConfig:
+        """从文件加载配置"""
+        if not self.config_file.exists():
+            return AppConfig()
+        
+        try:
+            with open(self.config_file, 'r', encoding='utf-8') as f:
+                data = json.load(f)
+            
+            return AppConfig(
+                api_key=data.get("api_key", ""),
+                model=data.get("model", "deepseek-chat"),
+                base_url=data.get("base_url", "https://api.deepseek.com")
+            )
+        except Exception:
+            return AppConfig()
+    
+    def exists(self) -> bool:
+        """检查配置文件是否存在"""
+        return self.config_file.exists()