Fix: unignore backend models package

.gitignore

@@ -1,2 +1,4 @@
 __pycache__
-models
+# Only ignore top-level models directory (for DL assets),
+# not Python packages named "models" deeper in the tree.
+/models

backend/py/app/models/__init__.py

@@ -0,0 +1,2 @@
+__all__ = []
+

backend/py/app/models/schemas.py

@@ -0,0 +1,37 @@
+from typing import Any, Dict, Literal, Optional
+
+from pydantic import BaseModel, Field
+
+
+class DetectionParams(BaseModel):
+    canny_low: Optional[int] = Field(None, ge=0, le=255)
+    canny_high: Optional[int] = Field(None, ge=0, le=255)
+    harris_k: Optional[float] = Field(None, ge=0.0, le=1.0)
+    harris_block: Optional[int] = Field(None, ge=1, le=16)
+    harris_ksize: Optional[int] = Field(None, ge=1, le=15)
+    hough_thresh: Optional[int] = Field(None, ge=1, le=500)
+    hough_min_len: Optional[int] = Field(None, ge=1, le=1000)
+    hough_max_gap: Optional[int] = Field(None, ge=0, le=200)
+    ellipse_min_area: Optional[int] = Field(None, ge=10, le=100000)
+    max_ellipses: Optional[int] = Field(None, ge=1, le=100)
+
+
+class DetectionRequest(BaseModel):
+    image: str = Field(..., description="Base64-encoded image (PNG/JPEG).")
+    params: Optional[DetectionParams] = None
+    mode: Literal["classical", "dl", "both"] = "classical"
+    compare: bool = False
+    dl_model: Optional[str] = Field(
+        None, description="Optional ONNX filename override from ./models."
+    )
+
+
+class DetectionResponse(BaseModel):
+    overlay: Optional[str] = None
+    overlays: Dict[str, Optional[str]]
+    features: Dict[str, Any]
+    timings: Dict[str, float]
+    fps_estimate: Optional[float] = None
+    model: Dict[str, Any]
+    models: Dict[str, Dict[str, Any]]
+