added child endpoint, ability to add and edit child as well as auto redirect to add-child page when user without child accesses home page

src/baby_monitor/models/child.py

@@ -0,0 +1,23 @@
+"""Child-related request and response models."""
+
+from datetime import datetime
+from pydantic import BaseModel, Field
+
+
+class CreateChildRequest(BaseModel):
+    """Request model for creating a child."""
+
+    name: str = Field(..., min_length=1, max_length=100)
+    birth_time: datetime
+    birth_weight: float = Field(..., gt=0, description="Birth weight in grams")
+
+
+class ChildResponse(BaseModel):
+    """Response model for child data."""
+
+    id: int
+    name: str
+    birth_time: datetime
+    birth_weight: float
+    user_id: int
+    created_at: datetime