Add Cloudflare R2 storage for admin asset uploads; v2.0.37

New uploads route to R2 with folder selection (uploads/images/guides/finished).
Existing local files continue to be served via express.static for backward compat.
Adds R2_ACCOUNT_ID, R2_ACCESS_KEY_ID, R2_SECRET_ACCESS_KEY, R2_BUCKET,
R2_PUBLIC_URL env vars. listUploadedAssets merges R2 objects + local files.

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

package.json

@@ -1,7 +1,7 @@
 {
   "name": "siteforge",
   "private": true,
-  "version": "2.0.36",
+  "version": "2.0.37",
   "type": "module",
   "scripts": {
     "dev": "vite",
@@ -13,6 +13,7 @@
     "preview": "vite preview"
   },
   "dependencies": {
+    "@aws-sdk/client-s3": "^3.1135.0",
     "@dnd-kit/core": "^6.3.1",
     "@dnd-kit/sortable": "^10.0.0",
     "@dnd-kit/utilities": "^3.2.2",