Add GTL price-traffic chart diagnostic

app/schemas/sr_level.py

@@ -40,3 +40,23 @@ class SRLevelResponse(BaseModel):
     zones: list[SRZoneResult] = []
     visible_levels: list[SRLevelResult] = []
     count: int
+
+
+class GateTargetLevelResult(BaseModel):
+    """A transient Gate Target Ladder proposal for diagnostic display."""
+
+    price_level: float
+    type: Literal["support", "resistance"]
+    strength: int = Field(ge=0, le=100)
+    detection_method: str
+    sources: list[str] = Field(default_factory=list)
+    traffic_count: int = Field(ge=0)
+
+
+class GateTargetLadderResponse(BaseModel):
+    """Volume-free Gate Target Ladder computed from current OHLCV history."""
+
+    symbol: str
+    levels: list[GateTargetLevelResult]
+    count: int
+    lookback_bars: int