refactor: move Bytescale upload logic to backend for security

backend/package.json

@@ -15,6 +15,7 @@
 	"license": "ISC",
 	"type": "module",
 	"dependencies": {
+		"@bytescale/sdk": "^3.53.0",
 		"@editorjs/editorjs": "^2.31.4",
 		"@editorjs/header": "^2.8.8",
 		"@editorjs/list": "^2.0.9",
@@ -27,6 +28,7 @@
 		"express-session": "^1.19.0",
 		"jsonwebtoken": "^9.0.3",
 		"multer": "^2.1.1",
+		"node-fetch": "^3.3.2",
 		"postmark": "^4.0.7",
 		"prisma": "^6.19.2",
 		"slugify": "^1.6.9"