fix(i18n): localize splash strings

src/pages/LoginPage.tsx

@@ -188,8 +188,8 @@ export function LoginPage() {
           /* 启动动画 */
           <div className={styles.splashContent}>
             <img src={INLINE_LOGO_JPEG} alt="CPAMC" className={styles.splashLogo} />
-            <h1 className={styles.splashTitle}>CLI Proxy API</h1>
-            <p className={styles.splashSubtitle}>Management Center</p>
+            <h1 className={styles.splashTitle}>{t('splash.title')}</h1>
+            <p className={styles.splashSubtitle}>{t('splash.subtitle')}</p>
             <div className={styles.splashLoader}>
               <div className={styles.splashLoaderBar} />
             </div>

src/pages/OAuthPage.tsx

@@ -190,7 +190,7 @@ export function OAuthPage() {
       await navigator.clipboard.writeText(url);
       showNotification(t('notification.link_copied'), 'success');
     } catch {
-      showNotification('Copy failed', 'error');
+      showNotification(t('notification.copy_failed'), 'error');
     }
   };