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/pages/labels.html

@@ -5,27 +5,42 @@
   body { margin: 0; background: #fff; }
   .label-sheet { margin: 0; }
 }
-.label-tag { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-weight: 700; font-size: 11pt; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
-.label-name { font-size: 8pt; color: #333; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+.label-tag { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-weight: 700; font-size: 11pt; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; max-width: 100%; }
+.label-name { font-size: 8pt; color: #333; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; max-width: 100%; }
+.label.format-barcode .label-text { text-align: center; }
 </style>
 
 <div class="print-toolbar d-flex flex-wrap align-items-center gap-3 p-3 border-bottom">
   <button class="btn btn-primary" onclick="window.print()"><i class="bi bi-printer"></i> Print</button>
   <span class="text-body-secondary">{{len .Labels}} label(s)</span>
-  <form method="get" class="d-flex align-items-center gap-2 ms-auto">
-    {{if .AssetID}}<input type="hidden" name="asset_id" value="{{.AssetID}}">{{end}}
-    {{if .FolderID}}<input type="hidden" name="folder_id" value="{{.FolderID}}">{{end}}
-    {{if .Recursive}}<input type="hidden" name="recursive" value="1">{{end}}
-    <label class="form-label mb-0 small text-body-secondary" for="labelTemplateSelect">Label sheet</label>
+  <form method="get" class="d-flex flex-wrap align-items-center gap-2 ms-auto">
+    {{if .AssetIDs}}<input type="hidden" name="asset_ids" value="{{.AssetIDs}}">{{end}}
+    {{if .FolderIDs}}<input type="hidden" name="folder_ids" value="{{.FolderIDs}}">{{end}}
+
+    <label class="form-label mb-0 small text-body-secondary" for="labelFormatSelect">Code</label>
+    <select class="form-select form-select-sm" id="labelFormatSelect" name="format" onchange="this.form.submit()">
+      <option value="qr" {{if eq .Format "qr"}}selected{{end}}>QR code (opens on scan)</option>
+      <option value="barcode" {{if eq .Format "barcode"}}selected{{end}}>Barcode (Code128)</option>
+    </select>
+
+    <label class="form-label mb-0 small text-body-secondary" for="labelTemplateSelect">Sheet</label>
     <select class="form-select form-select-sm" id="labelTemplateSelect" name="template" onchange="this.form.submit()">
       {{range $key := .TemplateKeys}}
       {{$t := index $.Templates $key}}
       <option value="{{$key}}" {{if eq $key $.Selected.Key}}selected{{end}}>{{$t.DisplayName}}</option>
       {{end}}
     </select>
+
+    <label class="form-label mb-0 small text-body-secondary" for="labelStartInput">Start at #</label>
+    <input type="number" class="form-control form-control-sm" id="labelStartInput" name="start" value="{{.StartPos}}" min="1" style="width: 70px" onchange="this.form.submit()">
   </form>
 </div>
 
+<p class="text-body-secondary small px-3 pt-2 mb-0">
+  Already used some labels off this sheet? Set "Start at #" to the next free position (counting left-to-right,
+  top-to-bottom) instead of wasting them and starting a new sheet.
+</p>
+
 {{if .Selected.Approximate}}
 <div class="alert alert-warning m-3">
   This layout's grid/margins aren't from a verified spec sheet - print one test page on plain paper and
@@ -34,10 +49,11 @@
 {{end}}
 
 <div class="label-sheet">
+  {{range .BlankCells}}<div class="label-blank"></div>{{end}}
   {{range .Labels}}
-  <div class="label">
-    <img src="{{.QRData}}" alt="QR code for {{.Asset.AssetTag}}">
-    <div class="min-w-0">
+  <div class="label format-{{$.Format}}">
+    <img src="{{.ImageData}}" alt="{{if eq $.Format "barcode"}}Barcode{{else}}QR code{{end}} for {{.Asset.AssetTag}}">
+    <div class="min-w-0 label-text">
       <div class="label-tag">{{.Asset.AssetTag}}</div>
       <div class="label-name">{{.Asset.Name}}</div>
     </div>