fix: 消除积分预检硬编码，统一使用 getRule() 动态读取

CoverDesign: 预检 COVER_POINTS=2 → getRule('cover_design')?.points || 2
SubtitleBurning: 预检 SUBTITLE_POINTS=2 → getRule('subtitle_burn')?.points || 2
VideoCompose: 预检 COMPOSE_POINTS=5 → getRule('compose')?.points || 5

确保预检口径与扣费口径一致，避免后端规则调整后出现余额误判

tauri-app/src/pages/VideoCreation/CoverDesign.tsx

@@ -248,10 +248,10 @@ export default function CoverDesign() {
     if (!projectId) {return;}
     if (!config.mainTitle.trim()) {return;}
 
-    const COVER_POINTS = 2;
+    const coverPoints = usePointStore.getState().getRule('cover_design')?.points || 2;
     await fetchBalance();
     const currentBalance = usePointStore.getState().balance;
-    if (currentBalance < COVER_POINTS) {
+    if (currentBalance < coverPoints) {
       setShowPointsModal(true);
       return;
     }
@@ -636,39 +636,41 @@ export default function CoverDesign() {
             onClick={handleGenerate}
             style={{ flex: 1 }}
           >
-            {isDesigning ? '生成中...' : `重新生成(${usePointStore.getState().getRule('cover_design')?.points || 2}积分)`}
+            {isDesigning
+              ? '生成中...'
+              : coverPath
+                ? `重新生成(${usePointStore.getState().getRule('cover_design')?.points || 2}积分)`
+                : `生成封面(${usePointStore.getState().getRule('cover_design')?.points || 2}积分)`}
           </button>
-          <button
-            className="btn btn-secondary"
-            onClick={async () => {
-              if (!coverPath) {
-                toast.info('请先生成封面');
-                return;
-              }
-              try {
-                const filename = coverPath.split(/[\\/]/).pop() || 'cover.png';
-                const targetPath = await save({
-                  defaultPath: filename,
-                  filters: [{ name: '图片', extensions: ['png'] }],
-                });
-                if (!targetPath) {return;}
-                const res = await invoke<{ code: number; data?: string; message: string }>('export_product', {
-                  sourcePath: coverPath,
-                  targetPath,
-                });
-                if (res.code === 200) {
-                  toast.success('封面导出成功');
-                } else {
-                  toast.error(res.message || '导出失败');
+          {coverPath && (
+            <button
+              className="btn btn-secondary"
+              onClick={async () => {
+                try {
+                  const filename = coverPath.split(/[\\/]/).pop() || 'cover.png';
+                  const targetPath = await save({
+                    defaultPath: filename,
+                    filters: [{ name: '图片', extensions: ['png'] }],
+                  });
+                  if (!targetPath) {return;}
+                  const res = await invoke<{ code: number; data?: string; message: string }>('export_product', {
+                    sourcePath: coverPath,
+                    targetPath,
+                  });
+                  if (res.code === 200) {
+                    toast.success('封面导出成功');
+                  } else {
+                    toast.error(res.message || '导出失败');
+                  }
+                } catch (e) {
+                  toast.error('导出失败');
                 }
-              } catch (e) {
-                toast.error('导出失败');
-              }
-            }}
-            style={{ flex: 1 }}
-          >
-            导出封面
-          </button>
+              }}
+              style={{ flex: 1 }}
+            >
+              导出封面
+            </button>
+          )}
         </div>
       </div>
 

tauri-app/src/pages/VideoCreation/SubtitleBurning.tsx

@@ -333,11 +333,11 @@ export default function SubtitleBurning() {
       return;
     }
 
-    // 积分预检：字幕烧录固定消耗 2 积分
-    const SUBTITLE_POINTS = 2;
+    // 积分预检：字幕烧录
+    const subtitlePoints = usePointStore.getState().getRule('subtitle_burn')?.points || 2;
     await fetchBalance();
     const currentBalance = usePointStore.getState().balance;
-    if (currentBalance < SUBTITLE_POINTS) {
+    if (currentBalance < subtitlePoints) {
       setShowPointsModal(true);
       return;
     }

tauri-app/src/pages/VideoCreation/VideoCompose.tsx

@@ -217,11 +217,11 @@ export default function VideoCompose() {
       return;
     }
 
-    // 前置积分检查：压制成片固定消耗 5 积分
-    const COMPOSE_POINTS = 5;
+    // 前置积分检查：压制成片
+    const composePoints = usePointStore.getState().getRule('compose')?.points || 5;
     await fetchBalance();
     const currentBalance = usePointStore.getState().balance;
-    if (currentBalance < COMPOSE_POINTS) {
+    if (currentBalance < composePoints) {
       setShowPointsModal(true);
       return;
     }
@@ -266,11 +266,13 @@ export default function VideoCompose() {
         useProgressStore.getState().update('正在混合背景音乐...');
         const bgmFullPath = bgmMusicPath;
         const mixRes = await invoke<{ code: number; data?: string; message: string }>('mix_bgm_to_video', {
-          videoPath: result,
-          bgmPath: bgmFullPath,
-          outputPath: result,
-          videoVolume: 1.0,
-          bgmVolume: (bgmVolume ?? 0.25),
+          args: {
+            videoPath: result,
+            bgmPath: bgmFullPath,
+            outputPath: result,
+            videoVolume: 1.0,
+            bgmVolume: (bgmVolume ?? 0.25),
+          },
         });
         if (mixRes.code !== 200) {
           console.warn('BGM 混合失败，使用无 BGM 版本:', mixRes.message);