feat: P3 配音模块标签体系 — 标签 CRUD + 素材打标 + tag_ids 筛选

- 新增 Tag 领域实体 + TagModel/AssetTagModel ORM 模型
- Alembic 迁移 030：tags 表 + asset_tags 关联表
- TagRepository 端口 + SQLAlchemy/InMemory 实现
- Asset.tag_ids 多对多关联替代原 JSON tags
- GET /tags / POST /tags / DELETE /tags/{tag_id} 标签 CRUD
- POST /assets/{asset_id}/tags 打标 / DELETE 取消标签
- GET /assets 新增 tag_ids 筛选参数（逗号分隔，取交集）
- 19 个单元测试全部通过

packages/adapters/sqlalchemy_impl/models.py

@@ -90,6 +90,29 @@ class AssetModel(Base):
     updated_at = Column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
 
 
+class TagModel(Base):
+    """标签 ORM 模型。"""
+
+    __tablename__ = "tags"
+
+    id = Column(String(36), primary_key=True)
+    user_id = Column(String(36), nullable=False, index=True)
+    name = Column(String(100), nullable=False)
+    created_at = Column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
+
+    __table_args__ = (UniqueConstraint("user_id", "name", name="uq_tags_user_name"),)
+
+
+class AssetTagModel(Base):
+    """素材-标签关联表 ORM 模型。"""
+
+    __tablename__ = "asset_tags"
+
+    asset_id = Column(String(36), primary_key=True)
+    tag_id = Column(String(36), primary_key=True)
+    created_at = Column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
+
+
 class EditTemplateModel(Base):
     """Phase 8 剪辑模板 ORM 模型