feat: Add PDF parser selection to Agent Begin and Await Response comp… (#13325)

### Issue: #12756

### What problem does this PR solve?

When users upload files through Agent's Begin or Await Response
components, the parsing is hardcoded to "Plain Text", ignoring all other
available parsers (DeepDOC, TCADP, Docling, MinerU, PaddleOCR). This PR
adds a PDF parser dropdown to these components so users can select the
appropriate parser for their file inputs.


### Changes

**Backend**
- `agent/component/fillup.py` - Added `layout_recognize` param to
`UserFillUpParam`, forwarded to `FileService.get_files()`
- `agent/component/begin.py` - Same forwarding in `Begin._invoke()`
- `agent/canvas.py` - Extract Begin's `layout_recognize` for `sys.files`
parsing, added param to `get_files_async()` / `get_files()`
- `api/db/services/file_service.py` - Added `layout_recognize` param to
`parse()` and `get_files()`, replacing hardcoded `"Plain Text"`
- `rag/app/naive.py` - Added `"plain text"` and `"tcadp parser"` aliases
to PARSERS dict to match dropdown values after `.lower()`

**Frontend**
- `web/src/pages/agent/form/begin-form/index.tsx` - Show
`LayoutRecognizeFormField` dropdown when file inputs exist
- `web/src/pages/agent/form/begin-form/schema.ts` - Added
`layout_recognize` to Zod schema
- `web/src/pages/agent/form/user-fill-up-form/index.tsx` - Same dropdown
for Await Response component


### Type of change

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

agent/component/begin.py

@@ -41,6 +41,7 @@ class Begin(UserFillUp):
         if self.check_if_canceled("Begin processing"):
             return
 
+        layout_recognize = self._param.layout_recognize or None
         for k, v in kwargs.get("inputs", {}).items():
             if self.check_if_canceled("Begin processing"):
                 return
@@ -52,7 +53,7 @@ class Begin(UserFillUp):
                     file_value = v["value"]
                     # Support both single file (backward compatibility) and multiple files
                     files = file_value if isinstance(file_value, list) else [file_value]
-                    v = FileService.get_files(files)
+                    v = FileService.get_files(files, layout_recognize=layout_recognize)
             else:
                 v = v.get("value")
             self.set_output(k, v)

agent/component/fillup.py

@@ -27,6 +27,7 @@ class UserFillUpParam(ComponentParamBase):
         super().__init__()
         self.enable_tips = True
         self.tips = "Please fill up the form"
+        self.layout_recognize = ""
 
     def check(self) -> bool:
         return True
@@ -61,6 +62,7 @@ class UserFillUp(ComponentBase):
                 content = re.sub(r"\{%s\}"%k, ans, content)
 
             self.set_output("tips", content)
+        layout_recognize = self._param.layout_recognize or None
         for k, v in kwargs.get("inputs", {}).items():
             if self.check_if_canceled("UserFillUp processing"):
                 return
@@ -71,7 +73,7 @@ class UserFillUp(ComponentBase):
                     file_value = v["value"]
                     # Support both single file (backward compatibility) and multiple files
                     files = file_value if isinstance(file_value, list) else [file_value]
-                    v = FileService.get_files(files)
+                    v = FileService.get_files(files, layout_recognize=layout_recognize)
             else:
                 v = v.get("value")
             self.set_output(k, v)