feat(File Management): Refactor File List API and Add Knowledge Base Document Initialization (#13914)

### What problem does this PR solve?

feat(File Management): Refactor File List API and Add Knowledge Base
Document Initialization

- Migrate the file list API endpoint from `/v1/file/list` to
`/api/v1/files` to align with the Python implementation.
- Add logic for initializing knowledge base documents; automatically
create the `.knowledgebase` folder and associated documents when
retrieving the root directory.
- Enhance parameter validation and error handling, including the
introduction of a new `CodeParamError` error code.
- Optimize the file list response structure to match the implementation
on the Python side.
- Update the Vite configuration to support proxying the new
`/api/v1/files` endpoint.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

web/vite.config.ts

@@ -49,7 +49,7 @@ export default defineConfig(({ mode }) => {
       },
     },
     hybrid: {
-      '^(/api/v1/memories)|^(/v1/user/info)|^(/v1/user/tenant_info)|^(/v1/tenant/list)|^(/v1/system/config)|^(/v1/user/login)|^(/v1/user/logout)':
+      '^(/api/v1/memories)|^(/v1/user/info)|^(/v1/user/tenant_info)|^(/v1/tenant/list)|^(/v1/system/config)|^(/v1/user/login)|^(/v1/user/logout)|^(/api/v1/files)':
         {
           target: 'http://127.0.0.1:9384/',
           changeOrigin: true,