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.

web/templates/partials/modals.html

@@ -111,7 +111,7 @@
   <div class="modal-dialog">
     <div class="modal-content">
       <div class="modal-header">
-        <h5 class="modal-title">Move Asset</h5>
+        <h5 class="modal-title" id="moveAssetModalTitle">Move Asset</h5>
         <button type="button" class="btn-close" data-bs-dismiss="modal"></button>
       </div>
       <div class="modal-body">
@@ -151,6 +151,28 @@
   </div>
 </div>
 
+<!-- Bulk status change (multi-select > Edit Status...) -->
+<div class="modal fade" id="bulkStatusModal" tabindex="-1">
+  <div class="modal-dialog">
+    <div class="modal-content">
+      <div class="modal-header">
+        <h5 class="modal-title" id="bulkStatusModalTitle">Edit Status</h5>
+        <button type="button" class="btn-close" data-bs-dismiss="modal"></button>
+      </div>
+      <div class="modal-body">
+        <label class="form-label">New Status</label>
+        <select class="form-select" id="bulkStatusSelect">
+          {{range .Statuses}}<option value="{{.ID}}">{{.Name}}</option>{{end}}
+        </select>
+      </div>
+      <div class="modal-footer">
+        <button type="button" class="btn btn-outline-secondary" data-bs-dismiss="modal">Cancel</button>
+        <button type="button" class="btn btn-primary" id="confirmBulkStatusBtn">Save</button>
+      </div>
+    </div>
+  </div>
+</div>
+
 <!-- Import CSV into a specific folder (right-click a folder > Import CSV...) -->
 <div class="modal fade" id="importModal" tabindex="-1">
   <div class="modal-dialog">