feat(price): detect quantity discounts via baseprice, show Disc. badge

GoMag sends baseprice (catalog price) alongside price (discounted).
When baseprice > price, the item is volume-discounted — skip ROA
price comparison and show amber "Disc." badge instead of false
mismatch. Strikethrough baseprice in price column for transparency.

Pipeline: parse baseprice → store in SQLite → skip in validation →
pass flag to frontend → render badge (desktop + mobile pill badge
with aria-label, opacity 0.6 for dark mode).

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

api/app/templates/base.html

@@ -168,7 +168,7 @@
 
     <script>window.ROOT_PATH = "{{ rp }}";</script>
     <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js"></script>
-    <script src="{{ rp }}/static/js/shared.js?v=33"></script>
+    <script src="{{ rp }}/static/js/shared.js?v=34"></script>
     <script>
     // Dark mode toggle
     function toggleDarkMode() {