fix: three post-review corrections

- Filter source tags from gallery overlay refresh in view-modal.js and bulk-select.js
- Fix split(':', 1) bug causing series name to render as "undefined"
- Offset reader quick-nav above floating page indicator to prevent overlap

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/static/style.css

@@ -2740,7 +2740,7 @@ body.select-mode .gallery-infinite-container {
 .reader-quick-nav {
   position: fixed;
   right: 1.5rem;
-  bottom: 1.5rem;
+  bottom: 5rem;
   display: flex;
   flex-direction: column;
   gap: 0.5rem;