fix: 预览生成标题参数改用title_config对象匹配后端Schema

- CreatePreviewRequest: 删除8个独立title_*字段,改为title_config对象
- useStep5Preview: generatePreview传参改为title_config嵌套结构
- 字段映射: titleSettings.size → title_config.font_size
- 修复标题配置被Pydantic忽略导致预览视频/封面无标题的问题

apps/web/src/api/generation/types.ts

@@ -13,15 +13,17 @@ export interface CreatePreviewRequest {
   video_title?: string
   duration?: number
   video_ratio?: string
-  /* 标题烧录参数（可选，传入后 ASS 渲染标题到预览视频中） */
-  title_text?: string
-  title_font?: string
-  title_size?: number
-  title_color?: string
-  title_position?: string
-  title_bold?: boolean
-  title_stroke?: boolean
-  title_shadow?: boolean
+  /* 标题烧录配置（可选，传入后 ASS 渲染标题到预览视频中） */
+  title_config?: {
+    text?: string
+    font?: string
+    font_size?: number
+    font_color?: string
+    position?: string
+    bold?: boolean
+    stroke?: boolean
+    shadow?: boolean
+  }
   bgm_config?: {
     enabled: boolean
     preset_id?: string

apps/web/src/pages/generate/hooks/useStep5Preview.ts

@@ -358,15 +358,19 @@ export function useStep5Preview({
           video_ratio: videoRatio,
           voice_ids: voiceIds && voiceIds.length > 0 ? voiceIds : undefined,
           voice_library_id: voiceLibraryId || undefined,
-          // 标题信息
-          title_text: titleSettings?.title || undefined,
-          title_font: titleSettings?.font || undefined,
-          title_size: titleSettings?.size || undefined,
-          title_color: titleSettings?.color || undefined,
-          title_position: titleSettings?.position || undefined,
-          title_bold: titleSettings?.bold || undefined,
-          title_stroke: titleSettings?.stroke || undefined,
-          title_shadow: titleSettings?.shadow || undefined,
+          // 标题烧录配置
+          title_config: titleSettings?.title
+            ? {
+                text: titleSettings.title,
+                font: titleSettings.font,
+                font_size: titleSettings.size,
+                font_color: titleSettings.color,
+                position: titleSettings.position,
+                bold: titleSettings.bold,
+                stroke: titleSettings.stroke,
+                shadow: titleSettings.shadow,
+              }
+            : undefined,
         })
 
         if (startTimeRef.current === 0) return