feat(llm): 新增 LLM 智能增强服务(Agnes client + 4 项 enrichment 任务 + admin API + migration)

backend/app/models/llm_setting.py

@@ -0,0 +1,50 @@
+"""LLM 设置(单行,owner 可编辑)。
+
+字段对应:
+  - 排版/分类/点评提示词(用户可改)
+  - 插图尺寸 + prompt 模板(用户可改)
+  - 总开关 enabled
+  - 模型名(默认指向 Agnes,但可改成任意 OpenAI 兼容端点)
+"""
+from __future__ import annotations
+
+from datetime import datetime
+
+from sqlalchemy import Boolean, DateTime, Integer, String, Text, func
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.database import Base
+
+
+class LlmSetting(Base):
+    __tablename__ = "llm_settings"
+
+    # 永远只有一行:id=1
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, default=1)
+
+    # === 提示词 ===
+    format_prompt: Mapped[str | None] = mapped_column(Text)
+    classify_prompt: Mapped[str | None] = mapped_column(Text)
+    commentary_prompt: Mapped[str | None] = mapped_column(Text)
+    image_prompt_template: Mapped[str | None] = mapped_column(Text)
+
+    # === 插图参数 ===
+    image_size: Mapped[str] = mapped_column(String(16), default="1024x768", nullable=False)
+
+    # === 模型 ===
+    chat_model: Mapped[str] = mapped_column(String(64), default="agnes-2.0-flash", nullable=False)
+    image_model: Mapped[str] = mapped_column(String(64), default="agnes-image-2.1-flash", nullable=False)
+
+    # === 限速 ===
+    interval_sec: Mapped[float] = mapped_column(default=2.0, nullable=False)
+
+    # === 总开关 ===
+    enabled: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)
+
+    # === 时间 ===
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False
+    )
+
+    def __repr__(self) -> str:
+        return f"<LlmSetting id={self.id} enabled={self.enabled}>"