fix(modal): provenance chips use tag_id, not legacy tag=<name>

The provenance section's chip hrefs (artist, post) still built
'/gallery?tag=${name}', which the gallery route silently ignores
since Task 10 switched to ?tag_id=<int>. So clicking the artist or
post chip from the modal rendered an unfiltered gallery.

Tag objects from /image/<id>/tags already include 'id', so the fix
is one line: chip.href = '/gallery?tag_id=${t.id}'.

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

app/static/js/view-modal.js

@@ -481,7 +481,7 @@ document.addEventListener('DOMContentLoaded', () => {
     tags.forEach(t => {
       const chip = document.createElement('a');
       chip.className = 'provenance-chip';
-      chip.href = `/gallery?tag=${encodeURIComponent(t.name)}`;
+      chip.href = `/gallery?tag_id=${t.id}`;
       chip.title = t.name;
       chip.dataset.tagName = t.name;
       chip.dataset.kind = t.kind;