Feat:update webhook component (#11739)

### What problem does this PR solve?
issue:
https://github.com/infiniflow/ragflow/issues/10427

https://github.com/infiniflow/ragflow/issues/8115

change:

- Support for Multiple HTTP Methods (POST / GET / PUT / PATCH / DELETE /
HEAD)
- Security Validation
  1. max_body_size
  2. IP whitelist
  3. rate limit
  4. token / basic / jwt authentication
- File Upload Support
- Unified Content-Type Handling
- Full Schema-Based Extraction & Type Validation
- Two Execution Modes: Immediately / Streaming


### Type of change

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

agent/component/begin.py

@@ -28,7 +28,7 @@ class BeginParam(UserFillUpParam):
         self.prologue = "Hi! I'm your smart assistant. What can I do for you?"
 
     def check(self):
-        self.check_valid_value(self.mode, "The 'mode' should be either `conversational` or `task`", ["conversational", "task"])
+        self.check_valid_value(self.mode, "The 'mode' should be either `conversational` or `task`", ["conversational", "task","Webhook"])
 
     def get_input_form(self) -> dict[str, dict]:
         return getattr(self, "inputs")