fix(P1): 一键生成模板调速不生效 - speed配置同步到playback_speed顶级字段

根因：模板的speed/playback_speed只写到clip.config里，但UnifiedRenderService
_resolve_clips读的是clip.playback_speed顶级字段，导致调速始终1.0x。

修复：
1. _VirtualClip新增playback_speed字段
2. _apply_template_clip_effects里将模板speed同步到clip.playback_speed

apps/worker/worker_app/tasks/generation.py

@@ -174,6 +174,7 @@ class _VirtualClip:
     start_time: float = 0.0
     duration: float = 0.0
     transition_effect: str = "cut"
+    playback_speed: float = 1.0
     status: str = "ready"
     config: dict[str, Any] = field(default_factory=dict)
 
@@ -302,6 +303,16 @@ def _apply_template_clip_effects(
                     existing_config[key] = template_clip_config[key]
             clip.config = existing_config
 
+            # 3. 调速：同步到 clip.playback_speed 顶级字段（渲染引擎读此字段）
+            template_speed = template_clip_config.get("playback_speed") or template_clip_config.get("speed")
+            if template_speed:
+                try:
+                    speed_val = float(template_speed)
+                    if speed_val > 0:
+                        clip.playback_speed = speed_val
+                except (ValueError, TypeError):
+                    pass
+
 
 def _build_plan_and_clips_from_task(
     task_id: str,