feat(analyzer): add Canadian postal code (CA_POSTAL_CODE) recognizer

[Joey239716]

Change Description

Adds CaPostalCodeRecognizer for Canadian postal codes (entity CA_POSTAL_CODE)
in the A1A 1A1 (letter, digit, letter, optional space, digit, letter, digit) format

• Two patterns: a higher-confidence match (0.4) for the canonical
  space-separated form, and a lower-confidence match (0.1) for the space-omitted
  form commonly seen in stored data.
• Encodes Canada Post letter rules: excludes D, F, I, O, Q, U everywhere, and
  W, Z as the first letter.
• Context: English and French context words (Canada is officially bilingual).
• Disabled by default, consistent with other country-specific recognizers.
• Registered in the predefined recognizers package (__init__.py) and
  default_recognizers.yaml (with country_code: ca), plus unit tests and
  documentation (supported_entities.md, CHANGELOG.md).

Issue reference

Fixes #2163

Checklist

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