feat(analyzer): add Korean bank account number recognizer (KR_BANK_ACCOUNT)

[juno-junho]

Change Description

Add KrBankAccountRecognizer (entity KR_BANK_ACCOUNT) under country_specific/korea/, registered in the predefined recognizer exports, default_recognizers.yaml (disabled by default, country_code: kr) and the supported entities docs.

Korean bank account numbers had no coverage. The patterns are ported from a production Korean PII-masking deployment, with conservative scores (no checksum exists for Korean accounts) and negative lookaheads for phone (010/070), RRN and date look-alikes. Plain 13-digit runs are deliberately left to KR_RRN's domain.

Tests: positive cases assert the best-scoring match per layout (the patterns overlap by design), and a look-alike table asserts zero matches for Korean phone numbers, RRN shapes, dates and short digit runs. The full analyzer suite (3047 tests) and ruff check pass.

Issue reference

Fixes #2214

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