Fix: validate URL scheme and resolved IP before crawling to prevent SSRF (#14090)

### What problem does this PR solve?

The POST /upload_info?url=<url> endpoint accepted a user-supplied URL
and passed it directly to AsyncWebCrawler without any validation. There
were no restrictions on URL scheme, destination hostname, or resolved IP
address. This allowed any authenticated user to instruct the server to
make outbound HTTP requests to internal infrastructure — including RFC
1918 private networks, loopback addresses, and cloud metadata services
such as http://169.254.169.254 — effectively using the server as a proxy
for internal network reconnaissance or credential theft.

This PR adds an SSRF guard (_validate_url_for_crawl) that runs before
any crawl is initiated. It enforces an allowlist of safe schemes
(http/https), resolves the hostname at validation time, and rejects any
URL whose resolved IP falls within a private or reserved network range.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

test/testcases/test_web_api/test_document_app/test_upload_info_unit.py

@@ -79,6 +79,7 @@ def _load_document_app_module(monkeypatch):
 @pytest.mark.p2
 def test_upload_info_rejects_mixed_inputs(monkeypatch):
     module = _load_document_app_module(monkeypatch)
+    monkeypatch.setattr(module, "assert_url_is_safe", lambda url: ("example.com", "93.184.216.34"))
     files = _DummyFiles({"file": [_DummyFile("a.txt")]})
     monkeypatch.setattr(module, "request", _DummyRequest(files=files, args={"url": "https://example.com/a.txt"}))
 
@@ -100,6 +101,7 @@ def test_upload_info_requires_file_or_url(monkeypatch):
 @pytest.mark.p2
 def test_upload_info_supports_url_single_and_multiple_files(monkeypatch):
     module = _load_document_app_module(monkeypatch)
+    monkeypatch.setattr(module, "assert_url_is_safe", lambda url: ("example.com", "93.184.216.34"))
     captured = []
 
     def fake_upload_info(user_id, file_obj, url=None):