fix: long unbroken transaction description broke Dashboard layout

Card had no min-width: 0, so as a direct CSS Grid child on the
Dashboard it would grow to fit nowrap (truncate) text instead of
letting the ellipsis kick in — classic grid blowout. Reproduced with
Playwright (scrollWidth 2143px vs 1440px viewport before the fix,
matches after). Fixing it on the shared Card primitive protects every
grid/flex layout that uses it, not just Dashboard.

frontend/package.json

@@ -1,7 +1,7 @@
 {
   "name": "aurum-frontend",
   "private": true,
-  "version": "0.15.3",
+  "version": "0.15.4",
   "type": "module",
   "scripts": {
     "dev": "vite",