Add HKID / Taiwan ID pattern to privacy filter for mixed-locale coverage

[BOOK318]

Good first issue — expand PII coverage.

The privacy filter (privacy filter ver 1.0/) already catches some ID patterns. Add or verify coverage for:

• Taiwan national ID format (one letter + nine digits)
• Passport-like patterns

Use only fake/sample IDs (e.g. A123456789 for Taiwan format).

Acceptance:

• New test cases with fake data
• npm test passes
• Pattern documented in a code comment if non-obvious