feat(knowledge): sk knowledge bulk-tag — batch retag entries by query/filter

[magicpro97]

User Story

As a developer, I want to retag/re-wing multiple knowledge entries at once after reorganising taxonomy.

Acceptance Criteria

• sk knowledge bulk-tag [--query T] [--wing W] [--room R] [--tag T] to select entries
• --add-tag TAG, --set-wing W, --set-room R as mutation flags
• Dry-run by default; --apply to commit changes
• Prints count of affected entries before writing
• Tests in test_fixes.py (15+)

Priority: MED