fix: 音频素材库卡片高度改为 fit-content，防止被网格拉伸

tauri-app/src/pages/ContentManagement/VoiceMaterialLibrary.tsx

@@ -437,8 +437,8 @@ export default function VoiceMaterialLibrary() {
         isLoadingMaterials ? (
           <p style={{ color: 'var(--text-secondary)' }}>加载中...</p>
         ) : (
-          <div style={{ display: 'flex', flexDirection: 'column', gap: 16, flex: 1 }}>
-            <div className="voice-list" style={{ display: 'grid', gridTemplateColumns: 'repeat(2, 1fr)', gap: 12, flex: 1 }}>
+          <div style={{ display: 'flex', flexDirection: 'column', gap: 16, flex: 1, overflow: 'auto' }}>
+            <div className="voice-list" style={{ display: 'grid', gridTemplateColumns: 'repeat(2, 1fr)', gap: 12, alignContent: 'start', alignItems: 'start' }}>
               {voiceMaterials.length === 0 && (
                 <div className="empty-state" style={{ gridColumn: '1 / -1', minHeight: 300 }}>
                   <div className="empty-state-icon">
@@ -466,7 +466,7 @@ export default function VoiceMaterialLibrary() {
                     alignItems: 'center',
                     justifyContent: 'space-between',
                     gap: 12,
-                    minHeight: 64,
+                    height: 'fit-content',
                   }}
                 >
                   <div style={{ flex: 1, minWidth: 0, display: 'flex', flexDirection: 'column', gap: 4 }}>