Feat: add SearXNG search tool to Agent (frontend + backend, i18n) (#9699)

### What problem does this PR solve?

This PR integrates SearXNG as a new search tool for Agents. It adds
corresponding form/config UI on the frontend and a new tool
implementation on the backend, enabling aggregated web searches via a
self-hosted SearXNG instance within chats/workflows. It also adds
multilingual copy to support internationalized presentation and
configuration guidance.

### Type of change

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

### What’s Changed
- Frontend: new SearXNG tool configuration, forms, and command wiring
  - Main changes under `web/src/pages/agent/`
- New components and form entries are connected to Agent tool selection
and workflow node configuration
- Backend: new tool implementation
- `agent/tools/searxng.py`: connects to a SearXNG instance and performs
search based on the provided instance URL and query parameters
- i18n updates
- Added/updated keys under `web/src/locales/`: `searXNG` and
`searXNGDescription`
- English reference in
[web/src/locales/en.ts](cci:7://file:///c:/Users/ruy_x/Work/CRSC/2025/Software_Development/2025.8/ragflow-pr/ragflow/web/src/locales/en.ts:0:0-0:0):
    - `searXNG: 'SearXNG'`
- `searXNGDescription: 'A component that searches via your provided
SearXNG instance URL. Specify TopN and the instance URL.'`
- Other languages have `searXNG` and `searXNGDescription` added as well,
but accuracy is only guaranteed for English, Simplified Chinese, and
Traditional Chinese.

---------

Co-authored-by: xurui <xurui@crscd.com.cn>

agent/tools/searxng.py

@@ -0,0 +1,156 @@
+#
+#  Copyright 2024 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+import logging
+import os
+import time
+from abc import ABC
+import requests
+from agent.tools.base import ToolMeta, ToolParamBase, ToolBase
+from api.utils.api_utils import timeout
+
+
+class SearXNGParam(ToolParamBase):
+    """
+    Define the SearXNG component parameters.
+    """
+
+    def __init__(self):
+        self.meta: ToolMeta = {
+            "name": "searxng_search",
+            "description": "SearXNG is a privacy-focused metasearch engine that aggregates results from multiple search engines without tracking users. It provides comprehensive web search capabilities.",
+            "parameters": {
+                "query": {
+                    "type": "string",
+                    "description": "The search keywords to execute with SearXNG. The keywords should be the most important words/terms(includes synonyms) from the original request.",
+                    "default": "{sys.query}",
+                    "required": True
+                },
+                "searxng_url": {
+                    "type": "string",
+                    "description": "The base URL of your SearXNG instance (e.g., http://localhost:4000). This is required to connect to your SearXNG server.",
+                    "required": False,
+                    "default": ""
+                }
+            }
+        }
+        super().__init__()
+        self.top_n = 10
+        self.searxng_url = ""
+
+    def check(self):
+        # Keep validation lenient so opening try-run panel won't fail without URL.
+        # Coerce top_n to int if it comes as string from UI.
+        try:
+            if isinstance(self.top_n, str):
+                self.top_n = int(self.top_n.strip())
+        except Exception:
+            pass
+        self.check_positive_integer(self.top_n, "Top N")
+
+    def get_input_form(self) -> dict[str, dict]:
+        return {
+            "query": {
+                "name": "Query",
+                "type": "line"
+            },
+            "searxng_url": {
+                "name": "SearXNG URL",
+                "type": "line",
+                "placeholder": "http://localhost:4000"
+            }
+        }
+
+
+class SearXNG(ToolBase, ABC):
+    component_name = "SearXNG"
+
+    @timeout(os.environ.get("COMPONENT_EXEC_TIMEOUT", 12))
+    def _invoke(self, **kwargs):
+        # Gracefully handle try-run without inputs
+        query = kwargs.get("query")
+        if not query or not isinstance(query, str) or not query.strip():
+            self.set_output("formalized_content", "")
+            return ""
+
+        searxng_url = (kwargs.get("searxng_url") or getattr(self._param, "searxng_url", "") or "").strip()
+        # In try-run, if no URL configured, just return empty instead of raising
+        if not searxng_url:
+            self.set_output("formalized_content", "")
+            return ""
+
+        last_e = ""
+        for _ in range(self._param.max_retries+1):
+            try:
+                # 构建搜索参数
+                search_params = {
+                    'q': query,
+                    'format': 'json',
+                    'categories': 'general',
+                    'language': 'auto',
+                    'safesearch': 1,
+                    'pageno': 1
+                }
+
+                # 发送搜索请求
+                response = requests.get(
+                    f"{searxng_url}/search",
+                    params=search_params,
+                    timeout=10
+                )
+                response.raise_for_status()
+                
+                data = response.json()
+                
+                # 验证响应数据
+                if not data or not isinstance(data, dict):
+                    raise ValueError("Invalid response from SearXNG")
+                
+                results = data.get("results", [])
+                if not isinstance(results, list):
+                    raise ValueError("Invalid results format from SearXNG")
+                
+                # 限制结果数量
+                results = results[:self._param.top_n]
+                
+                # 处理搜索结果
+                self._retrieve_chunks(results,
+                                      get_title=lambda r: r.get("title", ""),
+                                      get_url=lambda r: r.get("url", ""),
+                                      get_content=lambda r: r.get("content", ""))
+                
+                self.set_output("json", results)
+                return self.output("formalized_content")
+
+            except requests.RequestException as e:
+                last_e = f"Network error: {e}"
+                logging.exception(f"SearXNG network error: {e}")
+                time.sleep(self._param.delay_after_error)
+            except Exception as e:
+                last_e = str(e)
+                logging.exception(f"SearXNG error: {e}")
+                time.sleep(self._param.delay_after_error)
+
+        if last_e:
+            self.set_output("_ERROR", last_e)
+            return f"SearXNG error: {last_e}"
+
+        assert False, self.output()
+
+    def thoughts(self) -> str:
+        return """
+Keywords: {} 
+Searching with SearXNG for relevant results...
+                """.format(self.get_input().get("query", "-_-!"))