feat: #1768 节奏曲线模板多样化 — 8种预设 + 时长钳制 + 误差校验

变更：
- RHYTHM_TEMPLATES 从 6 种扩展到 8 种（新增 [2,2,1,1,2] 和 [3,2,1,2,1]）
- 修复 MIN_CLIP_DURATION 被重复定义为 1.0 的 bug（恢复为 2.0）
- plan_clip_durations 新增 asset_durations 参数，钳制最大片段时长 <= 素材可用时长 × 90%
- 新增时长总和误差校验（成片净时长与配音时长误差 <= 0.5s），超限时末段补偿修正
- edit_plan_service.apply_voice_duration_to_plan 传入素材时长参与钳制
- 48 个新增单元测试全部通过

向后兼容：asset_durations 默认 None，不影响现有调用方

apps/api/app/services/edit_plan_service.py

@@ -789,20 +789,22 @@ class EditPlanService:
         if plan and hasattr(plan, "config") and plan.config:
             rhythm_template = plan.config.get("rhythm_template")
 
+        # #1768：先获取素材时长，传入 plan_clip_durations 用于最大片段钳制
+        asset_ids = [c.asset_id for c in clips if c.asset_id]
+        durations = self.get_asset_durations(asset_ids)
+        asset_durations_for_plan = [durations.get(c.asset_id, 0.0) for c in clips]
+
         target = plan_clip_durations(
             len(clips),
             voice,
             transition_effects=[c.transition_effect for c in clips],
             transition_durations=[float(c.transition_duration or 0.0) for c in clips],
             rhythm_template=rhythm_template,
+            asset_durations=asset_durations_for_plan,
         )
         if not target:
             return None
 
-        # 素材时长（短素材起点钳 0）
-        asset_ids = [c.asset_id for c in clips if c.asset_id]
-        durations = self.get_asset_durations(asset_ids)
-
         clips_data: list[dict] = []
         for i, c in enumerate(clips):
             dur = float(target[i])
@@ -1210,7 +1212,7 @@ class EditPlanService:
         config_asset_ids_count = len((plan.config or {}).get("asset_ids", []))
         clips_with_asset_count = sum(1 for c in clips if c.asset_id)
         logger.info(
-            "can_generate 诊断: plan=%s status=%s total_clips=%d " "clips_with_asset=%d config_asset_ids_count=%d",
+            "can_generate 诊断: plan=%s status=%s total_clips=%d clips_with_asset=%d config_asset_ids_count=%d",
             plan_id,
             plan.status,
             len(clips),
@@ -1222,7 +1224,7 @@ class EditPlanService:
             config_asset_ids = (plan.config or {}).get("asset_ids", [])
             if config_asset_ids:
                 logger.warning(
-                    "can_generate 最后防线触发: plan=%s clips=%d 均无素材，" "从 config.asset_ids(%d个) 自动分配",
+                    "can_generate 最后防线触发: plan=%s clips=%d 均无素材，从 config.asset_ids(%d个) 自动分配",
                     plan_id,
                     len(clips),
                     len(config_asset_ids),
@@ -1254,7 +1256,7 @@ class EditPlanService:
                     return False, "没有可渲染的就绪片段，自动修复后仍未分配素材"
             else:
                 logger.warning(
-                    "can_generate 失败: plan=%s clips=%d 均无素材，" "且 config.asset_ids 为空，无法自动修复",
+                    "can_generate 失败: plan=%s clips=%d 均无素材，且 config.asset_ids 为空，无法自动修复",
                     plan_id,
                     len(clips),
                 )