feat(db): 0003 migration + LlmSetting/Source 模型加 blocklist_tags

- 新增 alembic 0003: sources.blocklist_tags + llm_settings.blocklist_tags(JSONB)
- 两层配置:全局(llm_settings) + per-source(sources),合并去重后注入 classify prompt
- 默认空数组,不影响存量数据;admin API 在下个 commit 暴露编辑入口

backend/app/models/llm_setting.py

@@ -11,6 +11,7 @@ from __future__ import annotations
 from datetime import datetime
 
 from sqlalchemy import Boolean, DateTime, Integer, String, Text, func
+from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import Mapped, mapped_column
 
 from app.database import Base
@@ -28,6 +29,13 @@ class LlmSetting(Base):
     commentary_prompt: Mapped[str | None] = mapped_column(Text)
     image_prompt_template: Mapped[str | None] = mapped_column(Text)
 
+    # === 全局屏蔽分类标签(如 ["体育", "娱乐"])===
+    # 与 sources.blocklist_tags 合并去重后注入 classify prompt;
+    # 命中则删文章(drop)
+    blocklist_tags: Mapped[list[str]] = mapped_column(
+        JSONB, nullable=False, default=list, server_default="[]"
+    )
+
     # === 插图参数 ===
     image_size: Mapped[str] = mapped_column(String(16), default="768x512", nullable=False)