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PBKDF2-SHA256 + 16-byte salt + 200k iterations on res.users. Format of the stored hash string is <salt_hex>$<digest_hex>. Field is manager-readable only (groups=group_fusion_plating_manager); helpers that need to read or write it use .sudo() internally so operator-level callers can still set/verify their own PIN. Adds set_tablet_pin / verify_tablet_pin / clear_tablet_pin model methods + action_open_tablet_pin_setup that triggers the OWL setup modal (Phase 6.2). Tests cover hash uniqueness, verify, clear with chatter post, and the 4-digit format guard. Tests verified on entech: -u fusion_plating_shopfloor --test-tags fp_tablet_pin Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>