feat(analyzer): add Danish CPR number recognizer

[WMOlsen]

Change Description

Adds a Danish CPR number (DK_CPR_NUMBER) predefined recognizer to presidio-analyzer. Disabled by default in default_recognizers.yaml, tagged country_code: dk.

• DK_CPR_NUMBER (DkCprRecognizer): the 10-digit Danish personnummer, format DDMMYY-SSSS (hyphenated) or DDMMYYSSSS (contiguous).
  • Date validation derives the full four-digit birth year from the official CPR century table (7th digit + two-digit year), so leap days are validated correctly (e.g. 290204 = 29 Feb 1904 is accepted, 290203 = 29 Feb 1903 is rejected).
  • Modulus-11 checksum (weights 4 3 2 7 6 5 4 3 2 1) is applied as confirmation only: a passing checksum promotes the match to full confidence, but a failing checksum never rejects the candidate. CPR-kontoret discontinued the mandatory modulus-11 control in 2007 because several birth dates had exhausted their supply of control-digit-valid sequence numbers, so numbers issued since then are not guaranteed to satisfy it. A hard checksum gate would silently drop valid personal data, which is the failure mode a PII detector must avoid.
  • Two \b-anchored patterns (hyphenated 0.5, contiguous 0.3); no boundary-less fallback, to avoid matching inside longer numeric strings.
• Updated CHANGELOG.md, docs/supported_entities.md, default_recognizers.yaml, and predefined_recognizers/__init__.py.
• Added tests/test_dk_cpr_recognizer.py; all cases pass locally. ruff check and ruff format --check pass on the changed files.

Known limitations: the contiguous 10-digit form can collide with other 10-digit numeric identifiers; this is mitigated by date validation, context words, and the lower 0.3 pattern score. Healthcare replacement numbers (erstatningsnumre, day + 60) are intentionally not matched, as they are a regional-system convention rather than CPR-register numbers. Space-separated forms (DDMMYY SSSS) are not matched.

Issue reference

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