refactor(js): tag-utils uses display_name and tag_id

getTagDisplayName is now a passthrough; post-refactor names are bare
and callers that need the character+fandom suffix pass tag.display_name
from the server. createTagChipHtml builds ?tag_id=<int> URLs and uses
display_name for the label. bulk-select.js callers pass display_name
directly.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/static/js/bulk-select.js

@@ -270,7 +270,7 @@
 
     dom.commonTags.innerHTML = tags.map(t => {
       const icon = getTagIcon(t.kind);
-      const display = getTagDisplayName(t.name, t.kind);
+      const display = t.display_name || t.name;
       const escapedName = escapeHtml(t.name);
       const escapedDisplay = escapeHtml(display);
       return `<span class="tag-chip removable" data-name="${escapedName}">
@@ -605,7 +605,7 @@
 
     dom.autocomplete.innerHTML = tags.map((t, i) => {
       const icon = getTagIcon(t.kind);
-      const displayName = getTagDisplayName(t.name, t.kind);
+      const displayName = t.display_name || t.name;
       return `<div class="tag-autocomplete-item" data-index="${i}" data-name="${escapeHtml(t.name)}">
         <span>${icon} ${escapeHtml(displayName)}</span>
         <span class="tag-kind">${t.kind || 'user'}</span>