Add /contacts and /calendar pages; email signature settings; v1.1.12

- /contacts: standalone page with hybrid contact list (submissions + manual entry), inline edit, search, archive
- /calendar: monthly release scheduling calendar reading/writing podcast checklist episode dates
- /email settings: editable signature panel; signature persisted server-side and injected into outgoing emails
- Move contacts out of /admin panel (now links to /contacts route)
- Partial PATCH for contact submissions (name, notes, archived independently)

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

package.json

@@ -1,7 +1,7 @@
 {
   "name": "siteforge",
   "private": true,
-  "version": "1.1.11",
+  "version": "1.1.12",
   "type": "module",
   "scripts": {
     "dev": "vite",