feat: сохранять ручные PN→LOT маппинги как lot_suggestion в qt_vendor_partnumber_seen

При сохранении vendor-spec строки с заполненным lot_mappings автоматически
отправляются на сервер и пишутся в новый столбец lot_suggestion. Столбец
хранит JSON-массив [{lot_name, qty}] — тот же формат, что qt_partnumber_book_items.lots_json.

Если миграция ещё не прошла (столбец отсутствует), приложение логирует WARN
и записывает строку без столбца; сбоя нет.

Контракт для инструмента создания partnumber-books описан в bible-local/11-lot-suggestions.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/services/sync/partnumber_seen.go

@@ -1,20 +1,31 @@
 package sync
 
 import (
+	"encoding/json"
 	"fmt"
 	"log/slog"
+	"strings"
 	"time"
 )
 
 // SeenPartnumber represents an unresolved vendor partnumber to report.
 type SeenPartnumber struct {
-	Partnumber  string
-	Description string
-	Ignored     bool
+	Partnumber    string
+	Description   string
+	Ignored       bool
+	LotSuggestion []LotSuggestionEntry // optional; set when user manually mapped PN → LOT in UI
+}
+
+// LotSuggestionEntry is one suggested LOT mapping for a vendor partnumber.
+// JSON shape mirrors qt_partnumber_book_items.lots_json: {"lot_name", "qty"}.
+type LotSuggestionEntry struct {
+	LotName string `json:"lot_name"`
+	Qty     int    `json:"qty"`
 }
 
 // PushPartnumberSeen inserts unresolved vendor partnumbers into qt_vendor_partnumber_seen on MariaDB.
-// Existing rows are left untouched: no updates to last_seen_at, is_ignored, or description.
+// When LotSuggestion is provided the column is updated too; if the column does not exist yet
+// (migration pending) the write is retried without it and a warning is logged — the app never panics.
 func (s *Service) PushPartnumberSeen(items []SeenPartnumber) error {
 	if len(items) == 0 {
 		return nil
@@ -30,7 +41,43 @@ func (s *Service) PushPartnumberSeen(items []SeenPartnumber) error {
 		if item.Partnumber == "" {
 			continue
 		}
-		err := mariaDB.Exec(`
+
+		if len(item.LotSuggestion) > 0 {
+			suggJSON, marshalErr := json.Marshal(item.LotSuggestion)
+			if marshalErr != nil {
+				slog.Error("partnumber_seen: failed to marshal lot_suggestion, skipping suggestion",
+					"partnumber", item.Partnumber, "error", marshalErr)
+				suggJSON = nil
+			}
+
+			if suggJSON != nil {
+				err = mariaDB.Exec(`
+					INSERT INTO qt_vendor_partnumber_seen
+						(source_type, vendor, partnumber, description, is_ignored, last_seen_at, lot_suggestion)
+					VALUES
+						('manual', '', ?, ?, ?, ?, ?)
+					ON DUPLICATE KEY UPDATE
+						lot_suggestion = VALUES(lot_suggestion),
+						last_seen_at   = NOW(3)
+				`, item.Partnumber, item.Description, item.Ignored, now, string(suggJSON)).Error
+
+				if err == nil {
+					continue
+				}
+
+				// Column not yet migrated — fall through to insert without lot_suggestion.
+				if !isUnknownColumnError(err) {
+					slog.Error("partnumber_seen: failed to upsert with lot_suggestion",
+						"partnumber", item.Partnumber, "error", err)
+					continue
+				}
+				slog.Warn("partnumber_seen: lot_suggestion column missing (migration pending), inserting without it",
+					"partnumber", item.Partnumber)
+			}
+		}
+
+		// Insert without lot_suggestion (baseline behaviour or fallback).
+		err = mariaDB.Exec(`
 			INSERT INTO qt_vendor_partnumber_seen
 				(source_type, vendor, partnumber, description, is_ignored, last_seen_at)
 			VALUES
@@ -40,10 +87,18 @@ func (s *Service) PushPartnumberSeen(items []SeenPartnumber) error {
 		`, item.Partnumber, item.Description, item.Ignored, now).Error
 		if err != nil {
 			slog.Error("failed to insert partnumber_seen", "partnumber", item.Partnumber, "error", err)
-			// Continue with remaining items
 		}
 	}
 
 	slog.Info("partnumber_seen pushed to server", "count", len(items))
 	return nil
 }
+
+// isUnknownColumnError returns true when MariaDB reports that a column does not exist.
+func isUnknownColumnError(err error) bool {
+	if err == nil {
+		return false
+	}
+	msg := strings.ToLower(err.Error())
+	return strings.Contains(msg, "unknown column") || strings.Contains(msg, "1054")
+}