fix: hide recipe variations button when locked instead of disabled+lock-badge (v0.78.1)

Was the one gated feature still shown as a clickable disabled button with a small lock icon overlay, opening an upgrade dialog on click. Every other gated feature (pairings, nutrition estimate, markdown export) hides entirely instead — brought this one in line and removed the now-dead locked/UpgradeDialog code from VariationsButton.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "epicure",
-  "version": "0.78.0",
+  "version": "0.78.1",
   "private": true,
   "scripts": {
     "dev": "pnpm --filter web dev",