feat: implement vendor spec BOM import and PN→LOT resolution (Phase 1)

- Migration 029: local_partnumber_books, local_partnumber_book_items,
  vendor_spec TEXT column on local_configurations
- Models: LocalPartnumberBook, LocalPartnumberBookItem, VendorSpec,
  VendorSpecItem with JSON Valuer/Scanner
- Repository: PartnumberBookRepository (GetActiveBook, FindLotByPartnumber,
  SaveBook/Items, ListBooks, CountBookItems)
- Service: VendorSpecResolver 3-step resolution (book → manual suggestion
  → unresolved) + AggregateLOTs with is_primary_pn qty logic
- Sync: PullPartnumberBooks append-only pull from qt_partnumber_books
- Handlers: VendorSpecHandler (GET/PUT/resolve/apply), PartnumberBooksHandler
- Routes: /api/configs/:uuid/vendor-spec*, /api/partnumber-books,
  /api/sync/partnumber-books, /partnumber-books page
- UI: 3 top-level tabs [Estimate][BOM вендора][Ценообразование]; Excel paste,
  PN resolution, inline LOT autocomplete, pricing table
- Bible: 03-database.md updated, 09-vendor-spec.md added

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

internal/localdb/models.go

@@ -103,6 +103,7 @@ type LocalConfiguration struct {
 	WarehousePricelistID  *uint                       `gorm:"index" json:"warehouse_pricelist_id,omitempty"`
 	CompetitorPricelistID *uint                       `gorm:"index" json:"competitor_pricelist_id,omitempty"`
 	OnlyInStock           bool                        `gorm:"default:false" json:"only_in_stock"`
+	VendorSpec             VendorSpec                  `gorm:"type:text" json:"vendor_spec,omitempty"`
 	Line                  int                         `gorm:"column:line_no;index" json:"line"`
 	PriceUpdatedAt        *time.Time                  `gorm:"type:timestamp" json:"price_updated_at,omitempty"`
 	CreatedAt             time.Time                   `json:"created_at"`
@@ -243,3 +244,70 @@ type PendingChange struct {
 func (PendingChange) TableName() string {
 	return "pending_changes"
 }
+
+// LocalPartnumberBook stores a version snapshot of the PN→LOT mapping book (pull-only from PriceForge)
+type LocalPartnumberBook struct {
+	ID        uint      `gorm:"primaryKey;autoIncrement" json:"id"`
+	ServerID  int       `gorm:"uniqueIndex;not null" json:"server_id"`
+	Version   string    `gorm:"not null" json:"version"`
+	CreatedAt time.Time `gorm:"not null" json:"created_at"`
+	IsActive  bool      `gorm:"not null;default:true" json:"is_active"`
+}
+
+func (LocalPartnumberBook) TableName() string {
+	return "local_partnumber_books"
+}
+
+// LocalPartnumberBookItem stores a single PN→LOT mapping within a book snapshot
+type LocalPartnumberBookItem struct {
+	ID          uint   `gorm:"primaryKey;autoIncrement" json:"id"`
+	BookID      uint   `gorm:"not null;index:idx_local_book_pn,priority:1" json:"book_id"`
+	Partnumber  string `gorm:"not null;index:idx_local_book_pn,priority:2" json:"partnumber"`
+	LotName     string `gorm:"not null" json:"lot_name"`
+	IsPrimaryPN bool   `gorm:"not null;default:false" json:"is_primary_pn"`
+	Description string `json:"description,omitempty"`
+}
+
+func (LocalPartnumberBookItem) TableName() string {
+	return "local_partnumber_book_items"
+}
+
+// VendorSpecItem represents a single row in a vendor BOM specification
+type VendorSpecItem struct {
+	SortOrder           int      `json:"sort_order"`
+	VendorPartnumber    string   `json:"vendor_partnumber"`
+	Quantity            int      `json:"quantity"`
+	Description         string   `json:"description,omitempty"`
+	UnitPrice           *float64 `json:"unit_price,omitempty"`
+	TotalPrice          *float64 `json:"total_price,omitempty"`
+	ResolvedLotName     string   `json:"resolved_lot_name,omitempty"`
+	ResolutionSource    string   `json:"resolution_source,omitempty"` // "book", "manual", "unresolved"
+	ManualLotSuggestion string   `json:"manual_lot_suggestion,omitempty"`
+}
+
+// VendorSpec is a JSON-encodable slice of VendorSpecItem
+type VendorSpec []VendorSpecItem
+
+func (v VendorSpec) Value() (driver.Value, error) {
+	if v == nil {
+		return nil, nil
+	}
+	return json.Marshal(v)
+}
+
+func (v *VendorSpec) Scan(value interface{}) error {
+	if value == nil {
+		*v = nil
+		return nil
+	}
+	var bytes []byte
+	switch val := value.(type) {
+	case []byte:
+		bytes = val
+	case string:
+		bytes = []byte(val)
+	default:
+		return errors.New("type assertion failed for VendorSpec")
+	}
+	return json.Unmarshal(bytes, v)
+}