Add email reminders to calendar episodes; v1.1.15

- Per-episode reminder select (1d/2d/3d/1wk/2wk before publish date)
- Server checks hourly; fires Resend email to admin on reminder day
- reminderSentAt persisted so reminders don't re-fire; cleared if date or setting changes
- Bell indicator on calendar chips; sent confirmation in edit popover

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

package.json

@@ -1,7 +1,7 @@
 {
   "name": "siteforge",
   "private": true,
-  "version": "1.1.14",
+  "version": "1.1.15",
   "type": "module",
   "scripts": {
     "dev": "vite",