feat: 后端 CRUD 完成（episodes + yearly_targets + users 管理 API）

backend/app/models/episode.py

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+"""
+节目期次模型 — SQLModel
+
+业务规则（.clinerules 5.3 软引用 + 快照模式）:
+  - editor_id 可空（离职编导）
+  - editor_name_snapshot 必填（历史导入也走快照）
+  - 查询历史作品：先 editor_id，回退 editor_name_snapshot 文本匹配
+"""
+
+from datetime import date, datetime
+
+from sqlalchemy import Column
+from sqlalchemy import DateTime as SADateTime
+from sqlalchemy import Text
+from sqlalchemy import Boolean as SABoolean
+from sqlalchemy import Integer as SAInteger
+from sqlalchemy import Numeric as SANumeric
+from sqlalchemy.sql import func as sa_func
+from sqlmodel import Field, SQLModel
+
+
+class Episode(SQLModel, table=True):
+    __tablename__ = "episodes"
+
+    id: int | None = Field(default=None, primary_key=True)
+    episode_number: int = Field(unique=True, index=True)
+    program_name: str = Field(max_length=200)
+    air_date: date
+
+    # 编导（软引用 + 快照双字段）
+    # 在职编导：editor_id 和 editor_name_snapshot 都填
+    # 离职编导：editor_id 留空，editor_name_snapshot 填姓名
+    editor_id: int | None = Field(default=None, foreign_key="users.id")
+    editor_name_snapshot: str = Field(max_length=100)
+
+    # 收视数据
+    # 注意：.clinerules 5.1 颜色只对 audience_share 上色
+    # audience_rating 只展示数字，不参与颜色判定
+    audience_share: float | None = Field(default=None)
+    audience_rating: float | None = Field(default=None)
+
+    # 重播相关
+    is_rerun: bool = Field(default=False)
+    original_episode_id: int | None = Field(default=None, foreign_key="episodes.id")
+    is_time_sensitive: bool = Field(default=False)
+
+    # 外拍信息
+    is_outdoor_shoot: bool = Field(default=False)
+    outdoor_contact_person: str | None = Field(default=None, max_length=100)
+    outdoor_contact_info: str | None = Field(default=None, max_length=200)
+
+    # 线索
+    lead_source: str | None = Field(default=None, max_length=300)
+
+    # 责编备注
+    notes: str | None = Field(default=None)
+
+    created_at: datetime | None = Field(
+        default=None,
+        sa_column=Column(SADateTime(timezone=True), nullable=False, server_default=sa_func.now()),
+    )
+    updated_at: datetime | None = Field(
+        default=None,
+        sa_column=Column(SADateTime(timezone=True), nullable=False, server_default=sa_func.now()),
+    )

backend/app/models/yearly_target.py

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+"""
+年度收视目标模型 — SQLModel
+
+业务规则（.clinerules 5.2 年度目标只增不改）:
+  - yearly_targets.year 有 UNIQUE 约束，数据库层已保证
+  - 代码端 INSERT 时只许 ON CONFLICT DO NOTHING，禁止 ON CONFLICT UPDATE
+  - 历史年份目标行绝不可被覆盖或删除
+  - 前端判颜色时按播出年份取对应年的目标，不是当前年份
+"""
+
+from datetime import date, datetime
+
+from sqlalchemy import Column
+from sqlalchemy import DateTime as SADateTime
+from sqlalchemy import Integer as SAInteger
+from sqlalchemy import Numeric as SANumeric
+from sqlalchemy.sql import func as sa_func
+from sqlmodel import Field, SQLModel
+
+
+class YearlyTarget(SQLModel, table=True):
+    __tablename__ = "yearly_targets"
+
+    id: int | None = Field(default=None, primary_key=True)
+    year: int = Field(unique=True, index=True)
+    base_target: float  # 基础目标
+    stretch_target: float  # 摸高目标
+    issued_date: date | None = Field(default=None)
+    notes: str | None = Field(default=None)
+
+    created_at: datetime | None = Field(
+        default=None,
+        sa_column=Column(SADateTime(timezone=True), nullable=False, server_default=sa_func.now()),
+    )