Refactor constants management to use Pydantic BaseModel for configuration

- Replaced module-level path variables in constants.py with a structured Pydantic Config class.
- Updated all relevant modules (train.py, augmentation.py, exports.py, dataset-visualiser.py, manual_run.py) to access paths through the new config structure.
- Fixed bugs related to image processing and model saving.
- Enhanced test infrastructure to accommodate the new configuration approach.

This refactor improves code maintainability and clarity by centralizing configuration management.

_docs/02_document/modules/inference_dto.md

@@ -0,0 +1,55 @@
+# Module: inference/dto
+
+## Purpose
+Data transfer objects for the inference subsystem: Detection, Annotation, and a local copy of AnnotationClass/WeatherMode.
+
+## Public Interface
+
+### Detection
+| Field | Type | Description |
+|-------|------|-------------|
+| `x` | float | Normalized center X |
+| `y` | float | Normalized center Y |
+| `w` | float | Normalized width |
+| `h` | float | Normalized height |
+| `cls` | int | Class ID |
+| `confidence` | float | Detection confidence score |
+| `overlaps(det2, iou_threshold) -> bool` | method | IoU-based overlap check |
+
+### Annotation
+| Field | Type | Description |
+|-------|------|-------------|
+| `frame` | numpy.ndarray | Video frame image |
+| `time` | int/float | Timestamp in the video |
+| `detections` | list[Detection] | Detected objects in this frame |
+
+### AnnotationClass (duplicate)
+Same as `dto/annotationClass.AnnotationClass` but with an additional `opencv_color` field (BGR tuple). Reads from `classes.json` relative to `inference/` parent directory.
+
+### WeatherMode (duplicate)
+Same as `dto/annotationClass.WeatherMode`.
+
+## Internal Logic
+- `Detection.overlaps()` computes IoU between two bounding boxes and returns True if above threshold.
+- `AnnotationClass` here adds `opencv_color` as a pre-computed BGR tuple from the hex color for efficient OpenCV rendering.
+
+## Dependencies
+- `json`, `enum`, `os.path` (stdlib)
+
+## Consumers
+inference/inference
+
+## Data Models
+Detection, Annotation, AnnotationClass, WeatherMode.
+
+## Configuration
+Reads `classes.json` from project root.
+
+## External Integrations
+None.
+
+## Security
+None.
+
+## Tests
+None.