feat(chart): M9-1 Chart DTO + Chart Service + Chart API（v3 §20）

- domain/entities/chart.py：ChartResult/OHLC/Volume/Series/EventMarker/ChartMetadata
  （adjust_mode + execution_price_basis 口径元数据）+ SelectionHit
- application/services/chart_service.py：个股 K线/量/MA 指标；显示层 qfq/hfq 折算
  （基于主口径 none 行情 × adjust_factor，绝回写研究数据）；回测个股视图把实际成交
  转 fills 标记并在显示口径不同时做坐标换算（v3 §20.3/§20.5）
- by-symbol 历史查询：SignalRepository/SelectionRepository.list_by_symbol（含溯源 id）
- api/charts.py：/stocks/{symbol}/chart|signals|selections、/backtests/{id}/stocks/{symbol}/chart
  |trades|positions
- tests/test_charts.py（指标/qfq-hfq 折算断言/回测 fills/API 集成+404）；全量 pytest 通过

backend/app/domain/entities/chart.py

@@ -0,0 +1,88 @@
+"""统一量化可视化 DTO（v3 §20 Chart Service）。
+
+原则：前端只展示本结构，不得自行重算选股/信号/成交（v3 §20.1）。
+价格口径：bars 已按请求 adjust 折算（显示层）；成交/信号标记与 K 线同坐标系；
+metadata 记录 adjust_mode 与回测执行价 basis，杜绝图表与回测口径混用（v3 §20.5）。
+"""
+
+from __future__ import annotations
+
+from datetime import date
+
+from pydantic import BaseModel, Field
+
+
+class OHLC(BaseModel):
+    time: date
+    open: float | None = None
+    high: float | None = None
+    low: float | None = None
+    close: float | None = None
+
+
+class VolumePoint(BaseModel):
+    time: date
+    value: float | None = None
+
+
+class SeriesPoint(BaseModel):
+    """指标/分数等 (时间, 值) 序列点。"""
+
+    time: date
+    value: float | None = None
+
+
+class EventMarker(BaseModel):
+    """K 线上可点击的事件标记（选股/信号/实际成交）。"""
+
+    time: date
+    kind: str = Field(
+        description="selection | signal_buy | signal_sell | signal_watch | fill_buy | fill_sell"
+    )
+    symbol: str = ""
+    price: float | None = None
+    score: float | None = None
+    text: list[str] = Field(default_factory=list, description="原因/说明（tooltip）")
+    ref_id: str | None = Field(default=None, description="关联 selection/signal 记录 id")
+
+
+class ChartMetadata(BaseModel):
+    symbol: str
+    name: str = ""
+    adjust_mode: str = Field(default="none", description="显示口径：none | qfq | hfq")
+    price_basis: str = Field(default="chart_display", description="显示价基准（显示层折算）")
+    execution_price_basis: str | None = Field(
+        default=None, description="回测执行价口径（如 none），与显示口径不同时用于解释"
+    )
+    start: date | None = None
+    end: date | None = None
+    bar_count: int = 0
+    indicator_windows: list[int] = Field(default_factory=list)
+
+
+class ChartResult(BaseModel):
+    """单只股票 / 回测个股的统一图表数据（v3 §20.2）。"""
+
+    metadata: ChartMetadata
+    bars: list[OHLC] = Field(default_factory=list)
+    volume: list[VolumePoint] = Field(default_factory=list)
+    indicators: dict[str, list[SeriesPoint]] = Field(default_factory=dict)
+    selections: list[EventMarker] = Field(default_factory=list)
+    signals: list[EventMarker] = Field(default_factory=list)
+    fills: list[EventMarker] = Field(default_factory=list)
+    holding_periods: list[dict] = Field(default_factory=list)
+    factor_values: dict[str, list[SeriesPoint]] = Field(default_factory=dict)
+    strategy_scores: dict[str, list[SeriesPoint]] = Field(default_factory=dict)
+    unimplemented: list[str] = Field(default_factory=list)
+
+
+class SelectionHit(BaseModel):
+    """个股在选股历史中的命中（by-symbol 查询）。"""
+
+    selection_id: str
+    as_of: date
+    method: str
+    symbol: str
+    rank: int
+    score: float
+    selection_reason: list[str] = Field(default_factory=list)

backend/app/domain/entities/signal.py

@@ -55,3 +55,14 @@ class SignalMeta(BaseModel):
     watch: int = 0
     sell: int = 0
     created_at: datetime | None = None
+
+
+class SignalHit(BaseModel):
+    """个股在信号历史中的命中（by-symbol 查询，供 Chart 标记）。"""
+
+    signal_id: str
+    signal_date: date
+    signal_type: str
+    score: float | None = None
+    price: float | None = None
+    trigger_reason: list[str] = Field(default_factory=list)

backend/app/domain/repositories/selection.py

@@ -10,6 +10,7 @@ from __future__ import annotations
 from datetime import date
 from typing import Protocol
 
+from app.domain.entities.chart import SelectionHit
 from app.domain.entities.selection import SelectionMeta, SelectionResult
 
 
@@ -27,3 +28,6 @@ class SelectionRepository(Protocol):
         limit: int = 20,
     ) -> list[SelectionMeta]:
         """历史选股元数据列表（按 created_at 倒序；可选 as_of/method 过滤）。"""
+
+    def list_by_symbol(self, symbol: str, limit: int = 50) -> list[SelectionHit]:
+        """该股在历史选股中的命中（Chart 标记用，含 as_of/rank/reason）。"""

backend/app/domain/repositories/signal.py

@@ -5,7 +5,7 @@ from __future__ import annotations
 from datetime import date
 from typing import Protocol
 
-from app.domain.entities.signal import SignalMeta, SignalResult
+from app.domain.entities.signal import SignalHit, SignalMeta, SignalResult
 
 
 class SignalRepository(Protocol):
@@ -17,3 +17,6 @@ class SignalRepository(Protocol):
     def list_recent(
         self, as_of: date | None = None, limit: int = 20
     ) -> list[SignalMeta]: ...
+
+    def list_by_symbol(self, symbol: str, limit: int = 50) -> list[SignalHit]:
+        """该股在历史信号中的命中（Chart 标记用，含 signal_id 溯源）。"""