feat(frontend): 完成品牌 SVG 与后台 Phase 1 基础切片

frontend/src/components/BrandLogo.tsx

@@ -1,17 +1,28 @@
-import logo from '@/assets/brand/logo-jieyou.png'
+import logoDark from '@/assets/brand/logo-dark.svg'
+import logoLight from '@/assets/brand/logo-light.svg'
+import logoSeal from '@/assets/brand/logo-seal.svg'
+
+export type BrandLogoVariant = 'light' | 'dark' | 'seal'
 
 interface BrandLogoProps {
   height?: number
+  variant?: BrandLogoVariant
   className?: string
 }
 
-export function BrandLogo({ height = 44, className }: BrandLogoProps) {
+const logoSources: Record<BrandLogoVariant, string> = {
+  light: logoLight,
+  dark: logoDark,
+  seal: logoSeal,
+}
+
+export function BrandLogo({ height = 44, variant = 'light', className }: BrandLogoProps) {
   return (
     <img
-      src={logo}
+      src={logoSources[variant]}
       alt="解忧商行 JIEYOU TRADING HOUSE"
       className={className}
-      style={{ height, width: 'auto', display: 'block', borderRadius: 4 }}
+      style={{ height, width: 'auto', display: 'block' }}
     />
   )
 }

frontend/src/components/PageLoading.tsx

@@ -0,0 +1,11 @@
+import { Spin } from 'antd'
+
+export function PageLoading({ tip = '正在核对商行账本…' }: { tip?: string }) {
+  return (
+    <div className="page-loading">
+      <Spin size="large" tip={tip}>
+        <div className="page-loading__placeholder" />
+      </Spin>
+    </div>
+  )
+}