feat: infinite scroll, HEIC support, likes fix, security & backup

- Fix liked hearts not showing after page reload (sync useEffect in CatCard)
- Replace pagination with infinite scroll (useInfiniteQuery + IntersectionObserver)
- Add HEIC/HEIF/AVIF image support with sharp conversion to JPEG on upload
- Validate MIME type alongside file extension to prevent spoofing
- Limit caption to 500 chars; increase upload size limit to 20MB
- Delete physical file from uploads/ when post is removed (cats + admin routes)
- Add WAL journal mode and graceful shutdown (SIGTERM/SIGINT) to db
- Add rate limiter for upload endpoint (10 req / 15 min)
- Add pre-deploy backup of data.db and uploads/ to deploy.sh (keeps last 10)
- Add plan_modernization.md with ideas for future improvements

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

deploy.sh

@@ -1,6 +1,36 @@
 #!/bin/bash
 set -e
 
+BACKUP_DIR="$HOME/cats-backups/$(date +%Y-%m-%d_%H-%M-%S)"
+
+echo "==> Creating backup at $BACKUP_DIR ..."
+mkdir -p "$BACKUP_DIR"
+
+# Backup database
+if [ -f server/data.db ]; then
+  cp server/data.db "$BACKUP_DIR/data.db"
+  echo "    ✓ data.db backed up"
+else
+  echo "    ⚠ data.db not found, skipping"
+fi
+
+# Backup uploads
+if [ -d server/uploads ] && [ "$(ls -A server/uploads 2>/dev/null)" ]; then
+  cp -r server/uploads "$BACKUP_DIR/uploads"
+  echo "    ✓ uploads/ backed up ($(ls server/uploads | wc -l) files)"
+else
+  echo "    ⚠ uploads/ empty or not found, skipping"
+fi
+
+# Keep only last 10 backups
+BACKUP_ROOT="$HOME/cats-backups"
+BACKUP_COUNT=$(ls -1 "$BACKUP_ROOT" | wc -l)
+if [ "$BACKUP_COUNT" -gt 10 ]; then
+  ls -1t "$BACKUP_ROOT" | tail -n +11 | xargs -I{} rm -rf "$BACKUP_ROOT/{}"
+  echo "    ✓ Old backups pruned (kept last 10)"
+fi
+
+echo ""
 echo "==> Pulling latest changes..."
 git pull
 
@@ -11,10 +41,12 @@ echo "==> Installing client dependencies..."
 npm install --prefix client
 
 echo "==> Building client..."
-npm run build
+npm run build --prefix client
 
 echo "==> Restarting PM2 process..."
 sudo pm2 restart cats
 sudo pm2 save
 
+echo ""
 echo "==> Done! Site updated at http://cats.heagbokat-server.ru"
+echo "    Backup saved to: $BACKUP_DIR"