fixed cookmate local recipe image import - #4820

Implemented the proper fix so Cookmate .mcb local photos are imported during normal import (no separate API pass needed).
Changes
cookbook/integration/cookmate.py:68-98 — Rewrote the image import step:

• Reads and loads the photo directly from the .mcb archive via self.safe_read(), falling back to a basename match if the stored path differs slightly.
• Falls back to the remote fetch only when no local image was found.
• Uses is not None checks instead of lxml truth-testing. This mattered: lxml 6.x reports elements containing only text (like images/a.jpg) as falsy, so a truthy-test would silently skip them. It also removes the AttributeError on self-closing empty elements.
• Detects the filetype (get_filetype) so PNG/WebP photos keep their format.
  cookbook/integration/integration.py:191 — Sets self.import_zip = import_zip in the Cookmate branch of do_import (same pattern already used by the Gourmet integration), so get_recipe_from_file can reach the archive.
  cookbook/tests/other/test_cookmate_integration.py — New tests covering: local image from archive, remote imageurl fallback (mock safe_request), and empty/self-closing / elements (no crash, no image).