Deduplicate vendor seen by partnumber and fix vendor mappings list

bible/history.md

@@ -5,6 +5,33 @@
 
 ---
 
+## 2026-02-20: Seen Registry Deduplication by Partnumber
+
+### Decision
+
+Changed `qt_vendor_partnumber_seen` semantics to one row per `partnumber` (vendor/source are no longer part of uniqueness).
+
+### Rationale
+
+- Eliminates duplicate seen rows when the same partnumber appears both with vendor and without vendor.
+- Keeps ignore behavior consistent regardless of vendor presence.
+- Simplifies operational cleanup and prevents re-creation of vendor/no-vendor duplicates.
+
+### Constraints
+
+- `partnumber` is now the unique key in seen registry.
+- Ignore checks are resolved by `partnumber` only.
+- Stock provenance must be preserved (`source_type='stock'`) when stock data exists for the partnumber.
+
+### Files
+
+- Migration: `migrations/025_dedup_vendor_seen_by_partnumber.sql`
+- Service: `internal/services/stock_import.go`
+- Service: `internal/services/vendor_mapping.go`
+- Model: `internal/models/lot.go`
+
+---
+
 ## 2026-02-18: Global Vendor Partnumber Mapping
 
 ### Decision