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/web/handlers_assets.go

@@ -169,6 +169,31 @@ func (a *App) handleAssetCheckout(w http.ResponseWriter, r *http.Request) {
 	jsonOK(w, map[string]any{"id": id, "assigned_user_id": req.AssignedUserID})
 }
 
+type assetStatusRequest struct {
+	StatusID int64 `json:"status_id"`
+}
+
+// handleAssetSetStatus changes only an asset's status - used by the bulk
+// "Edit Status" multi-select action so it doesn't have to resend every
+// other field the way a full PATCH does.
+func (a *App) handleAssetSetStatus(w http.ResponseWriter, r *http.Request) {
+	id, err := pathID(r, "id")
+	if err != nil {
+		jsonErr(w, http.StatusBadRequest, err)
+		return
+	}
+	var req assetStatusRequest
+	if err := readJSON(r, &req); err != nil {
+		jsonErr(w, http.StatusBadRequest, err)
+		return
+	}
+	if err := a.Assets.SetStatus(r.Context(), id, req.StatusID); err != nil {
+		jsonErr(w, http.StatusInternalServerError, err)
+		return
+	}
+	jsonOK(w, map[string]any{"id": id, "status_id": req.StatusID})
+}
+
 type assetQuantityRequest struct {
 	Delta int `json:"delta"`
 }