Make re-engagement email tiers configurable from admin; v1.1.20

Day thresholds and per-tier subject/body/CTA are now editable in the
Email Templates panel. Tier keys are position-based (t1/t2/t3) so
changing day values never re-sends emails already fired.

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

package.json

@@ -1,7 +1,7 @@
 {
   "name": "siteforge",
   "private": true,
-  "version": "1.1.19",
+  "version": "1.1.20",
   "type": "module",
   "scripts": {
     "dev": "vite",