Bulk multi-select actions, barcode format, batch printing, site name on login

Multi-select (Ctrl/Cmd+click toggle, Shift+click range, right-click the
active selection for bulk actions - same conventions as a native file
manager):
- Print Labels (N) / Export CSV (N) for any mix of individually-picked
  assets and whole folders. Labels/export now take asset_ids/folder_ids
  instead of a single asset_id/folder_id.
- Edit Status..., Check Out..., Duplicate, Move to..., and Delete, bulk
  versions of the existing single-asset actions. Checkout/Move modals
  were generalized to accept an array of ids instead of just one; status
  editing got its own lightweight POST /app/assets/{id}/status endpoint
  (assets.SetStatus) so a bulk status change doesn't need to resend every
  other field the way a full PATCH would.

Labels:
- Choose QR (a /scan/<tag> URL, for a phone camera) or Code128 barcode
  (the bare Asset ID, for a USB scanner typing into the search box) via a
  format selector on the print page. New barcodeDataURI using
  github.com/boombuler/barcode alongside the existing QR generator.
- "Start at #" lets printing resume partway into an already-used sheet
  instead of wasting it on a fresh one.
- Added the Avery 5260 label template (same grid as 5160, rounded
  corners, so it isn't flagged approximate).

Also: the configured Site Name now shows on the login page too, not just
the authenticated navbar.

internal/assets/csv.go

@@ -290,13 +290,8 @@ func (s *Store) Export(ctx context.Context, w io.Writer, f ListFilter) error {
 	if err != nil {
 		return err
 	}
-
 	cw := csv.NewWriter(w)
-	header := []string{"Asset ID", "Name", "Item Type", "Folder", "Status", "Assigned User", "Notes", "Quantity", "Created At", "Updated At"}
-	for _, k := range fieldDefs {
-		header = append(header, cfColPrefix+k)
-	}
-	if err := cw.Write(header); err != nil {
+	if err := writeAssetHeader(cw, fieldDefs); err != nil {
 		return err
 	}
 
@@ -312,19 +307,7 @@ func (s *Store) Export(ctx context.Context, w io.Writer, f ListFilter) error {
 			if err != nil {
 				return err
 			}
-			row := []string{
-				a.AssetTag, a.Name, a.ItemTypeName, folderPathString(a.FolderPath), a.StatusName, a.AssignedUsername, a.Notes,
-				strconv.Itoa(a.Quantity),
-				a.CreatedAt.Format("2006-01-02 15:04:05"), a.UpdatedAt.Format("2006-01-02 15:04:05"),
-			}
-			values := map[string]string{}
-			for _, fv := range a.CustomFields {
-				values[fv.Def.FieldKey] = fv.Value
-			}
-			for _, k := range fieldDefs {
-				row = append(row, values[k])
-			}
-			if err := cw.Write(row); err != nil {
+			if err := writeAssetRow(cw, a, fieldDefs); err != nil {
 				return err
 			}
 		}
@@ -337,6 +320,56 @@ func (s *Store) Export(ctx context.Context, w io.Writer, f ListFilter) error {
 	return cw.Error()
 }
 
+// ExportByIDs writes exactly the given assets (in the given order) as CSV -
+// used for a multi-select "Export CSV" batch that doesn't map onto a single
+// ListFilter (an arbitrary mix of individually-picked assets and whole
+// folders).
+func (s *Store) ExportByIDs(ctx context.Context, w io.Writer, ids []int64) error {
+	fieldDefs, err := s.allFieldKeys(ctx)
+	if err != nil {
+		return err
+	}
+	cw := csv.NewWriter(w)
+	if err := writeAssetHeader(cw, fieldDefs); err != nil {
+		return err
+	}
+	for _, id := range ids {
+		a, err := s.Get(ctx, id)
+		if err != nil {
+			continue
+		}
+		if err := writeAssetRow(cw, a, fieldDefs); err != nil {
+			return err
+		}
+	}
+	cw.Flush()
+	return cw.Error()
+}
+
+func writeAssetHeader(cw *csv.Writer, fieldDefs []string) error {
+	header := []string{"Asset ID", "Name", "Item Type", "Folder", "Status", "Assigned User", "Notes", "Quantity", "Created At", "Updated At"}
+	for _, k := range fieldDefs {
+		header = append(header, cfColPrefix+k)
+	}
+	return cw.Write(header)
+}
+
+func writeAssetRow(cw *csv.Writer, a *models.Asset, fieldDefs []string) error {
+	row := []string{
+		a.AssetTag, a.Name, a.ItemTypeName, folderPathString(a.FolderPath), a.StatusName, a.AssignedUsername, a.Notes,
+		strconv.Itoa(a.Quantity),
+		a.CreatedAt.Format("2006-01-02 15:04:05"), a.UpdatedAt.Format("2006-01-02 15:04:05"),
+	}
+	values := map[string]string{}
+	for _, fv := range a.CustomFields {
+		values[fv.Def.FieldKey] = fv.Value
+	}
+	for _, k := range fieldDefs {
+		row = append(row, values[k])
+	}
+	return cw.Write(row)
+}
+
 func folderPathString(path []models.BreadcrumbItem) string {
 	names := make([]string, len(path))
 	for i, p := range path {