feat: 预览数量 preview_count 上限校验 + Worker 并发提升至 4

- CreatePreviewGenerationTaskRequest 新增 preview_count 字段（1-10，默认1）
- 路由日志增加 preview_count 记录
- Docker Compose Worker 并发默认从 1 提升至 4
- Worker 资源限制调整为 4C8G 以支持并行渲染
- 新增 11 个单元测试覆盖 preview_count 校验及并发配置

apps/api/app/api/routes/generation_preview.py

@@ -270,10 +270,11 @@ def create_preview_generation_task(
     """
     user_id = authenticated_user.user.id
     logger.info(
-        "[预览生成] 接收请求: user_id=%s, template_id=%s, asset_count=%d",
+        "[预览生成] 接收请求: user_id=%s, template_id=%s, asset_count=%d, preview_count=%d",
         user_id,
         request.template_id,
         len(request.asset_ids),
+        request.preview_count,
     )
 
     # 预检查队列限流

apps/api/app/schemas/generation_task.py

@@ -146,6 +146,12 @@ class CreatePreviewGenerationTaskRequest(BaseModel):
         default_factory=dict,
         description="自定义BGM配置，覆盖模板BGM设置。支持 enabled/source/asset_id/preset_id/audio_url/volume 等字段",
     )
+    preview_count: int = Field(
+        default=1,
+        ge=1,
+        le=10,
+        description="预览视频生成数量，范围 1-10，默认 1",
+    )
 
     @model_validator(mode="after")
     def _check_template_id(self) -> "CreatePreviewGenerationTaskRequest":

infra/docker/compose.yml

@@ -15,7 +15,7 @@
 #   API_PORT         - API 端口映射 (staging: 8000, production: 8001)
 #   WEB_PORT         - Web 端口映射 (staging: 3001, production: 3002)
 #   GENERATED_FILES_HOST_DIR - 生成文件的主机目录
-#   WORKER_CONCURRENCY        - Worker 并发数 (默认: 1)
+#   WORKER_CONCURRENCY        - Worker 并发数 (默认: 4)
 #   WORKER_MAX_TASKS_PER_CHILD - Worker 每个子进程最大任务数 (默认: 100)
 #
 # 重要: 
@@ -109,7 +109,7 @@ services:
     environment:
       APP_ENV: ${APP_ENV:-staging}
       APP_VERSION: ${APP_VERSION:-unknown}
-      WORKER_CONCURRENCY: ${WORKER_CONCURRENCY:-1}
+      WORKER_CONCURRENCY: ${WORKER_CONCURRENCY:-4}
       WORKER_MAX_TASKS_PER_CHILD: ${WORKER_MAX_TASKS_PER_CHILD:-100}
       GENERATED_FILES_DIR: /app/generated
       GENERATED_FILES_URL_PREFIX: /generated-files
@@ -136,14 +136,15 @@ services:
     # 资源限制建议（生产环境建议启用）
     # =========================================
     # 注意: Worker 需要处理视频，建议分配更多资源
+    # 并发 4 时需要 4C8G 以上，确保视频渲染不 OOM
     deploy:
       resources:
         limits:
-          cpus: '2.0'
-          memory: 2g
+          cpus: '4.0'
+          memory: 8g
         reservations:
-          cpus: '0.5'
-          memory: 1G
+          cpus: '1.0'
+          memory: 2G
 
   # =========================================
   # Web 服务（Nginx + 前端静态文件）

tests/unit/test_1286_preview_count_validation.py

@@ -0,0 +1,130 @@
+"""预览数量 preview_count 校验测试。
+
+验证 CreatePreviewGenerationTaskRequest 中 preview_count 字段：
+- 默认值为 1
+- 范围 1-10
+- 超出范围报错
+- Worker 并发配置验证
+"""
+
+import pytest
+
+
+class TestPreviewCountValidation:
+    """preview_count 字段校验"""
+
+    def test_default_preview_count_is_1(self):
+        """默认 preview_count 为 1"""
+        from app.schemas.generation_task import CreatePreviewGenerationTaskRequest
+
+        req = CreatePreviewGenerationTaskRequest(
+            template_id="tmpl_123",
+            asset_ids=["asset_1"],
+        )
+        assert req.preview_count == 1
+
+    def test_preview_count_min_valid(self):
+        """preview_count=1 合法"""
+        from app.schemas.generation_task import CreatePreviewGenerationTaskRequest
+
+        req = CreatePreviewGenerationTaskRequest(
+            template_id="tmpl_123",
+            asset_ids=["asset_1"],
+            preview_count=1,
+        )
+        assert req.preview_count == 1
+
+    def test_preview_count_max_valid(self):
+        """preview_count=10 合法（上限）"""
+        from app.schemas.generation_task import CreatePreviewGenerationTaskRequest
+
+        req = CreatePreviewGenerationTaskRequest(
+            template_id="tmpl_123",
+            asset_ids=["asset_1"],
+            preview_count=10,
+        )
+        assert req.preview_count == 10
+
+    def test_preview_count_middle_value(self):
+        """preview_count=5 合法"""
+        from app.schemas.generation_task import CreatePreviewGenerationTaskRequest
+
+        req = CreatePreviewGenerationTaskRequest(
+            template_id="tmpl_123",
+            asset_ids=["asset_1"],
+            preview_count=5,
+        )
+        assert req.preview_count == 5
+
+    def test_preview_count_zero_raises(self):
+        """preview_count=0 报错（低于下限）"""
+        from app.schemas.generation_task import CreatePreviewGenerationTaskRequest
+        from pydantic import ValidationError
+
+        with pytest.raises(ValidationError):
+            CreatePreviewGenerationTaskRequest(
+                template_id="tmpl_123",
+                asset_ids=["asset_1"],
+                preview_count=0,
+            )
+
+    def test_preview_count_negative_raises(self):
+        """preview_count=-1 报错"""
+        from app.schemas.generation_task import CreatePreviewGenerationTaskRequest
+        from pydantic import ValidationError
+
+        with pytest.raises(ValidationError):
+            CreatePreviewGenerationTaskRequest(
+                template_id="tmpl_123",
+                asset_ids=["asset_1"],
+                preview_count=-1,
+            )
+
+    def test_preview_count_exceeds_max_raises(self):
+        """preview_count=11 报错（超过上限 10）"""
+        from app.schemas.generation_task import CreatePreviewGenerationTaskRequest
+        from pydantic import ValidationError
+
+        with pytest.raises(ValidationError):
+            CreatePreviewGenerationTaskRequest(
+                template_id="tmpl_123",
+                asset_ids=["asset_1"],
+                preview_count=11,
+            )
+
+    def test_preview_count_large_value_raises(self):
+        """preview_count=100 报错"""
+        from app.schemas.generation_task import CreatePreviewGenerationTaskRequest
+        from pydantic import ValidationError
+
+        with pytest.raises(ValidationError):
+            CreatePreviewGenerationTaskRequest(
+                template_id="tmpl_123",
+                asset_ids=["asset_1"],
+                preview_count=100,
+            )
+
+
+class TestWorkerConcurrencyConfig:
+    """Worker 并发配置验证"""
+
+    def test_default_worker_concurrency_is_4(self):
+        """Worker 默认并发为 4"""
+        from packages.config import WorkerSettings
+
+        settings = WorkerSettings()
+        assert settings.worker_concurrency == 4
+
+    def test_worker_concurrency_configurable(self):
+        """Worker 并发可通过环境变量配置"""
+        from packages.config import WorkerSettings
+
+        settings = WorkerSettings(worker_concurrency=8)
+        assert settings.worker_concurrency == 8
+
+    def test_worker_concurrency_is_int(self):
+        """Worker 并发为整数类型"""
+        from packages.config import WorkerSettings
+
+        settings = WorkerSettings()
+        assert isinstance(settings.worker_concurrency, int)