Get Similar Parts For Quote

For each part in the quote, return up to k most similar past parts.

Anchors are restricted to past quotes that are QUOTED or APPROVED, is_human_reviewed=True, and have a non-null unit_price on the corresponding line item. The cohort is further filtered to the same machining process + material so a CNC part doesn't anchor on sheet-metal history.

The response is always well-formed: parts with no fingerprint or no historical anchors return anchors=[] with n_anchors=0 (no 404). Used by the admin quote-review UI to anchor pricing decisions on historical analogs.