feat: ревизия до обновления цен + короткие ссылки /:code для опти

- При нажатии «обновить цены» создаётся ревизия текущего состояния
  («до обновления цен») через новый эндпоинт POST /api/configs/:uuid/snapshot,
  затем saveConfig создаёт ревизию с новыми ценами
- Роут GET /:code → редирект на /projects/:uuid по коду опти (регистронезависимо)
- Валидация кода опти: только URL-безопасные символы [A-Za-z0-9._-]
  (бэкенд + клиентская проверка + подсказка в форме)

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

internal/services/local_configuration.go

@@ -423,6 +423,13 @@ func (s *LocalConfigurationService) RefreshPrices(uuid string, ownerUsername str
 		}
 	}
 
+	// Capture fingerprint of the current state before any mutations.
+	preRefreshFP, err := localdb.BuildConfigurationSpecPriceFingerprint(localCfg)
+	if err != nil {
+		return nil, fmt.Errorf("build pre-refresh fingerprint: %w", err)
+	}
+	preRefreshCfg := *localCfg
+
 	// Update prices for all items from pricelist
 	updatedItems := make(localdb.LocalConfigItems, len(localCfg.Items))
 	for i, item := range localCfg.Items {
@@ -462,6 +469,18 @@ func (s *LocalConfigurationService) RefreshPrices(uuid string, ownerUsername str
 	localCfg.UpdatedAt = now
 	localCfg.SyncStatus = "pending"
 
+	// Before saving the new prices, snapshot the pre-refresh state so the revision
+	// history shows a clear before/after for every price update.
+	postRefreshFP, err := localdb.BuildConfigurationSpecPriceFingerprint(localCfg)
+	if err != nil {
+		return nil, fmt.Errorf("build post-refresh fingerprint: %w", err)
+	}
+	if preRefreshFP != postRefreshFP {
+		if err := s.snapshotPreRefreshTx(&preRefreshCfg, ownerUsername); err != nil {
+			return nil, fmt.Errorf("snapshot pre-refresh state: %w", err)
+		}
+	}
+
 	cfg, err := s.saveWithVersionAndPending(localCfg, "update", ownerUsername)
 	if err != nil {
 		return nil, fmt.Errorf("refresh prices with version: %w", err)
@@ -820,6 +839,13 @@ func (s *LocalConfigurationService) RefreshPricesNoAuth(uuid string, pricelistSe
 		}
 	}
 
+	// Capture fingerprint of the current state before any mutations.
+	preRefreshFP, err := localdb.BuildConfigurationSpecPriceFingerprint(localCfg)
+	if err != nil {
+		return nil, fmt.Errorf("build pre-refresh fingerprint: %w", err)
+	}
+	preRefreshCfg := *localCfg
+
 	// Update prices for all items from pricelist
 	updatedItems := make(localdb.LocalConfigItems, len(localCfg.Items))
 	for i, item := range localCfg.Items {
@@ -859,6 +885,18 @@ func (s *LocalConfigurationService) RefreshPricesNoAuth(uuid string, pricelistSe
 	localCfg.UpdatedAt = now
 	localCfg.SyncStatus = "pending"
 
+	// Before saving the new prices, snapshot the pre-refresh state so the revision
+	// history shows a clear before/after for every price update.
+	postRefreshFP, err := localdb.BuildConfigurationSpecPriceFingerprint(localCfg)
+	if err != nil {
+		return nil, fmt.Errorf("build post-refresh fingerprint: %w", err)
+	}
+	if preRefreshFP != postRefreshFP {
+		if err := s.snapshotPreRefreshTx(&preRefreshCfg, ""); err != nil {
+			return nil, fmt.Errorf("snapshot pre-refresh state: %w", err)
+		}
+	}
+
 	cfg, err := s.saveWithVersionAndPending(localCfg, "update", "")
 	if err != nil {
 		return nil, fmt.Errorf("refresh prices without auth with version: %w", err)
@@ -866,6 +904,16 @@ func (s *LocalConfigurationService) RefreshPricesNoAuth(uuid string, pricelistSe
 	return cfg, nil
 }
 
+// SnapshotCurrentState creates a revision of the current configuration state without modifying it.
+// Called before a client-side price refresh so the revision history has a clear before/after.
+func (s *LocalConfigurationService) SnapshotCurrentState(uuid string) error {
+	localCfg, err := s.localDB.GetConfigurationByUUID(uuid)
+	if err != nil {
+		return ErrConfigNotFound
+	}
+	return s.snapshotPreRefreshTx(localCfg, "")
+}
+
 // UpdateServerCount updates server count and recalculates total price without creating a new version.
 func (s *LocalConfigurationService) UpdateServerCount(configUUID string, serverCount int) (*models.Configuration, error) {
 	if serverCount < 1 {
@@ -1432,12 +1480,25 @@ func (s *LocalConfigurationService) appendVersionTx(
 	localCfg *localdb.LocalConfiguration,
 	operation string,
 	createdBy string,
+) (*localdb.LocalConfigurationVersion, error) {
+	return s.appendVersionTxNote(tx, localCfg, operation, createdBy, "")
+}
+
+func (s *LocalConfigurationService) appendVersionTxNote(
+	tx *gorm.DB,
+	localCfg *localdb.LocalConfiguration,
+	operation string,
+	createdBy string,
+	noteOverride string,
 ) (*localdb.LocalConfigurationVersion, error) {
 	snapshot, err := s.buildConfigurationSnapshot(localCfg)
 	if err != nil {
 		return nil, fmt.Errorf("build snapshot: %w", err)
 	}
 	changeNote := fmt.Sprintf("%s via local-first flow", operation)
+	if noteOverride != "" {
+		changeNote = noteOverride
+	}
 
 	var createdByPtr *string
 	if createdBy != "" {
@@ -1478,6 +1539,35 @@ func (s *LocalConfigurationService) appendVersionTx(
 	return nil, fmt.Errorf("%w: exceeded retries for %s", ErrVersionConflict, localCfg.UUID)
 }
 
+// snapshotPreRefreshTx creates a revision of the current configuration state before a price
+// refresh so the history clearly shows what existed before prices were updated.
+// Called only when prices are about to change (fingerprints differ).
+func (s *LocalConfigurationService) snapshotPreRefreshTx(localCfg *localdb.LocalConfiguration, createdBy string) error {
+	return s.localDB.DB().Transaction(func(tx *gorm.DB) error {
+		var locked localdb.LocalConfiguration
+		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
+			Where("uuid = ?", localCfg.UUID).
+			First(&locked).Error; err != nil {
+			if errors.Is(err, gorm.ErrRecordNotFound) {
+				return ErrConfigNotFound
+			}
+			return fmt.Errorf("lock row for pre-refresh snapshot: %w", err)
+		}
+
+		version, err := s.appendVersionTxNote(tx, localCfg, "update", createdBy, "до обновления цен")
+		if err != nil {
+			return fmt.Errorf("append pre-refresh version: %w", err)
+		}
+
+		if err := tx.Model(&localdb.LocalConfiguration{}).
+			Where("uuid = ?", localCfg.UUID).
+			Update("current_version_id", version.ID).Error; err != nil {
+			return fmt.Errorf("set current_version_id for pre-refresh snapshot: %w", err)
+		}
+		return nil
+	})
+}
+
 func (s *LocalConfigurationService) buildConfigurationSnapshot(localCfg *localdb.LocalConfiguration) (string, error) {
 	return localdb.BuildConfigurationSnapshot(localCfg)
 }