feat(cps): 淘宝活动落地页图做活——每活动关联图,运营上传/选已有

- model: cps_activity.image_url + 迁移 cps_activity_image 回填存量淘宝活动为现有图
- admin: 新建淘宝活动必传图(上传 /upload-image 或选已有 /activity-images),存绝对 URL
- 落地页 cps_redirect: 按 link→activity 取图展示,缺图兜底默认图,img src 经 html.escape
- media: save_cps_image + to_abs_media_url(基于 CPS_REDIRECT_BASE,跨域 admin-web 可显示)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/admin/schemas/cps.py

@@ -52,6 +52,7 @@ class CpsActivityOut(BaseModel):
     act_id: str | None = None
     product_view_sign: str | None = None
     payload: str | None = None  # 淘宝淘口令 / 京东链接
+    image_url: str | None = None  # 淘宝落地页图(绝对 URL)
     status: str
     remark: str | None = None
     created_at: datetime
@@ -65,6 +66,8 @@ class CpsActivityCreate(BaseModel):
     product_view_sign: str | None = Field(default=None, max_length=128)
     # 淘宝:整段淘口令文本 / 京东:推广链接
     payload: str | None = Field(default=None, max_length=4096)
+    # 淘宝落地页图(绝对/相对 URL;淘宝必填,由 router 校验)
+    image_url: str | None = Field(default=None, max_length=512)
     remark: str | None = Field(default=None, max_length=256)