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)

internal/common/error_code.go

@@ -31,6 +31,7 @@ const (
 	CodeResourceExhausted      ErrorCode = 107
 	CodePermissionError        ErrorCode = 108
 	CodeAuthenticationError    ErrorCode = 109
+	CodeParamError             ErrorCode = 110
 	CodeLicenseValid           ErrorCode = 320
 	CodeLicenseInactiveError   ErrorCode = 321
 	CodeLicenseExpiredError    ErrorCode = 322
@@ -59,6 +60,7 @@ var errorMessages = map[ErrorCode]string{
 	CodeResourceExhausted:      "Resource exhausted",
 	CodePermissionError:        "Permission denied",
 	CodeAuthenticationError:    "Authentication failed",
+	CodeParamError:             "Invalid parameters",
 	CodeLicenseValid:           "License valid",
 	CodeLicenseInactiveError:   "License inactive",
 	CodeLicenseExpiredError:    "License expired",