fix(banners): save relative storage paths so admin preview survives refresh

Uploads were stored as host-specific URLs and a force-reload could wipe a just-saved image, leaving a broken dark-theme preview.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/model/appBanners.ts

@@ -90,11 +90,11 @@ function parseSlider(raw: unknown): IBenefits[] {
   return []
 }
 
-export function parseAppBanners(value: string | null | undefined): AppBannersValue {
+export function parseAppBanners(value: string | Record<string, unknown> | null | undefined): AppBannersValue {
   const fallback = emptyAppBanners()
   if (!value) return fallback
   try {
-    const parsed = JSON.parse(value)
+    const parsed = typeof value === 'string' ? JSON.parse(value) : value
     if (!parsed || typeof parsed !== 'object') return fallback
 
     // فرمت قدیمی: فقط آرایهٔ اسلایدر (header_banner)