5e3e6b5319
Shop-floor sign-off currently makes operators redraw a signature every time, and the drawing is discarded (reports read x_fc_signature_image). Spec: use the saved Plating Signature (one-tap confirm-with-preview); draw once when absent and persist it to x_fc_signature_image so future sign-offs + reports reuse it. Tablet-workspace scope; no model/migration. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>