contentimport 11.0.x-dev

First release of the 11.0.x branch. Requires Drupal 10.3 or later, or Drupal 11.

Security hardening
- Sample CSVs are generated on request and the import log uses the Drupal
logger; nothing is written to the public files directory any more.
- Text is saved only with formats the importing user may use (no forced Full HTML).
- Node create/update access is checked and the entity is validated for every row;
updates are limited to the selected content type.
- Vocabularies are never created from CSV data; terms are created only in the
field's target vocabularies.
- Missing users are created only when explicitly enabled by a user with
"Administer users", and always as blocked accounts.
- Image values must be plain file names inside public:///images/.

Drupal 10.3 / 11 compatibility
- Import runs in a chunked batch (25 rows per request).
- Logic moved to the contentimport.importer service; the unprefixed global
helper functions were removed.
- No deprecated core APIs; PHP 8.4-safe CSV parsing.
- Automated tests and GitLab CI added.

Upgrading from 10.0.x
- Text formats are chosen on the import form instead of always Full HTML.
- langcode is optional; only nodeid is required when updating.
- Empty cells clear the field when updating.
- The old sites/default/files/contentimportlog.txt and .csv files are no
longer created and can be deleted.
See README.md for details.