feat: 新增题图上传接口和排播接口

backend/app/models/cover_settings.py

@@ -0,0 +1,28 @@
+"""
+题图设置模型 — SQLModel
+
+只存当前展示的一张题图，不动 episodes 表。
+"""
+
+from datetime import datetime
+
+from sqlalchemy import Column
+from sqlalchemy import DateTime as SADateTime
+from sqlalchemy import Integer as SAInteger
+from sqlalchemy import Text
+from sqlalchemy.sql import func as sa_func
+from sqlmodel import Field, SQLModel
+
+
+class CoverSettings(SQLModel, table=True):
+    __tablename__ = "cover_settings"
+
+    id: int | None = Field(default=None, primary_key=True)
+    key: str = Field(default="dashboard_cover", max_length=50)
+    cover_path: str | None = Field(default=None)        # 当前题图文件路径
+    episode_number: int | None = Field(default=None)   # 关联期次号
+    episode_title: str | None = Field(default=None)    # 关联期次节目名
+    updated_at: datetime | None = Field(
+        default=None,
+        sa_column=Column(SADateTime(timezone=True), nullable=False, server_default=sa_func.now()),
+    )