[refactor] engines: use datetime.fromisoformat instead of datetime.strptime where possible (#6394)

Refactor engines that parse ISO 8601 dates with strptime to use
fromisoformat instead. In most cases this is a direct replacement of
strptime(text, "format") with fromisoformat(text).

For engines where the source has a trailing "Z" that strptime consumed
as a literal (e.g. "%Y-%m-%dT%H:%M:%S.%fZ" in huggingface.py), add
rstrip("Z") to keep the output naive and preserve the existing behavior.

In sogou.py the date is extracted with a regular expression, which can
yield strings like "2026-7-11". strptime accepts this via its format
string, but fromisoformat does not. To preserve the existing behavior
and satisfy the format fromisoformat expects, add zero-padding for the
month and day.

Closes: #6098
---------
Signed-off-by: OneVth <onebrotravel@gmail.com>

searx/engines/boardreader.py

@@ -104,7 +104,7 @@ def response(resp: "SXNG_Response") -> EngineResults:
                 title=_remove_keyword_marker(result["Subject"]),
                 content=_remove_keyword_marker(result["Text"]),
                 url=result["Url"],
-                publishedDate=datetime.strptime(result["Published"], "%Y-%m-%d %H:%M:%S"),
+                publishedDate=datetime.fromisoformat(result["Published"]),
                 metadata=gettext.gettext("Posted by {author}").format(author=result["Author"]),
             )
         )