Rewrite README to accurately describe the app; bump to v1.0.2

Replaces outdated portfolio/project-cards description with accurate
documentation of the podcast/ministry site: features, all env vars,
routes, API endpoints, persistent data paths, and admin capabilities.

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

package.json

@@ -1,7 +1,7 @@
 {
   "name": "siteforge",
   "private": true,
-  "version": "1.0.1",
+  "version": "1.0.2",
   "type": "module",
   "scripts": {
     "dev": "vite",