feat(auth): 登录页改为 ymb 品牌并支持后台配置背景图

lib/l10n/app_en.arb

@@ -1,6 +1,6 @@
 {
   "@@locale": "en",
-  "appName": "FruitShorts",
+  "appName": "ymb",
   "demo": "DEMO",
   "homeHeadline": "Watch now",
   "homeSubtitle": "Free short drama preview.",
@@ -19,7 +19,7 @@
   "searchCancel": "Cancel",
   "featured": "Featured",
   "recommended": "Recommended",
-  "fruitShortsBrand": "FruitShorts",
+  "fruitShortsBrand": "ymb",
   "comingSoon": "Coming soon",
   "authLegal": "By continuing, you agree to the Terms of Service and Privacy Policy.",
   "authLegalLead": "By continuing, you agree to the",
@@ -408,8 +408,8 @@
   "genreDramaMystery": "Drama · Mystery",
   "continueWatchingHeading": "CONTINUE WATCHING",
   "preferencesHeading": "PREFERENCES",
-  "brandMark": "FRUITSHORTS",
-  "shareFooter": "FruitShorts",
+  "brandMark": "YMB",
+  "shareFooter": "ymb",
   "shortsTab": "Shorts",
   "myListTab": "My List",
   "watchFull": "Watch Full",
@@ -789,7 +789,7 @@
   "offlineDownloads": "Downloads",
   "watchPreferences": "Watch preferences",
   "contactSupport": "Contact support",
-  "vipBrandName": "FruitShorts VIP",
+  "vipBrandName": "VIP",
   "vipOpenNow": "Get VIP",
   "vipBenefitFree": "Free full access",
   "vipBenefitNoAds": "Ad-free viewing",
@@ -851,6 +851,7 @@
   "dataUnavailable": "—",
   "commonQuestions": "Common questions",
   "aboutUs": "About us",
+  "aboutBrandName": "Your mini business",
   "aboutDescription": "A focused, immersive place to watch short dramas.",
   "versionLabel": "Version {version}",
   "@versionLabel": {