refactor(prompt): extract file path logic and implement auto-import on first launch (#214)

- Extract prompt file path logic to dedicated prompt_files module
- Refactor PromptService to use centralized path resolution
- Implement auto-import for existing prompt files on first startup
- Add comprehensive unit tests for auto-import functionality

src-tauri/src/lib.rs

@@ -10,6 +10,7 @@ mod gemini_config; // 新增
 mod init_status;
 mod mcp;
 mod prompt;
+mod prompt_files;
 mod provider;
 mod services;
 mod settings;