feat(prompts): add prompts loader and configuration management

- Implemented a new prompts loader in `loader.go` to manage prompt templates and configurations.
- Introduced caching mechanism for prompt configurations to optimize loading.
- Added functions to apply platform-specific prompt template overrides.
- Created unit tests in `loader_test.go` to validate prompt configuration loading and reloading behavior.
- Ensured that the last valid configuration is retained in case of errors during reload.

apps/browser-extension/src/adapters/toutiaohao.ts

@@ -199,7 +199,7 @@ async function publishToutiaohao(context: AdapterContext): Promise<PlatformPubli
     trends_writing_tag: "0",
     claim_exclusive: "0",
     info_source: JSON.stringify({
-      source_type: 3,
+      source_type: 5,
       source_author_uid: "",
       time_format: "",
       position: {},