Add initial backend structure with models, utilities, and settings management

- Introduced .gitignore to exclude common Python artifacts and IDE files.
- Added contour models for contour generation.
- Implemented cryptographic utilities for data encryption and decryption.
- Created CSV metadata model for handling wafer data.
- Developed time-indexed data segment model.
- Established local settings model for application configuration.
- Added Z-wafer data models and parser for CSV file handling.
- Implemented Marching Squares algorithm for contour generation.

backend/zwafer_models.py

@@ -0,0 +1,28 @@
+from dataclasses import dataclass, field
+from datetime import datetime
+from typing import Dict, List, Optional
+
+
+# ===== Sensor Geometry =====
+@dataclass
+class Sensor:
+    label: str
+    x: float
+    y: float
+
+
+# ===== Data Row =====
+@dataclass
+class DataRecord:
+    time: float
+    values: List[float] = field(default_factory=list)
+
+
+# ===== Parsed Z-Wafer Container =====
+@dataclass
+class ZWaferData:
+    date: datetime = field(default_factory=lambda: datetime.min)
+    serial: Optional[str] = None
+    header: Dict[str, str] = field(default_factory=dict)
+    sensors: List[Sensor] = field(default_factory=list)
+    csv_headers: List[str] = field(default_factory=list)