feat: API docs for /files (#24423)

Signed-off-by: -LAN- <laipz8200@outlook.com>

api/controllers/files/__init__.py

@@ -1,9 +1,20 @@
 from flask import Blueprint
+from flask_restx import Namespace
 
 from libs.external_api import ExternalApi
 
-bp = Blueprint("files", __name__)
-api = ExternalApi(bp)
+bp = Blueprint("files", __name__, url_prefix="/files")
 
+api = ExternalApi(
+    bp,
+    version="1.0",
+    title="Files API",
+    description="API for file operations including upload and preview",
+    doc="/docs",  # Enable Swagger UI at /files/docs
+)
+
+files_ns = Namespace("files", description="File operations")
 
 from . import image_preview, tool_files, upload
+
+api.add_namespace(files_ns)