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/convert_annotations.md

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+# Module: convert-annotations
+
+## Purpose
+Standalone script that converts annotation files from external formats (Pascal VOC XML, oriented bounding box text) to YOLO format.
+
+## Public Interface
+
+| Function | Signature | Returns | Description |
+|----------|-----------|---------|-------------|
+| `convert` | `(folder, dest_folder, read_annotations, ann_format)` | — | Generic converter: reads images + annotations from folder, writes YOLO format to dest |
+| `minmax2yolo` | `(width, height, xmin, xmax, ymin, ymax) -> tuple` | (cx, cy, w, h) | Converts pixel min/max coords to normalized YOLO center format |
+| `read_pascal_voc` | `(width, height, s: str) -> list[str]` | YOLO label lines | Parses Pascal VOC XML, maps class names to IDs, outputs YOLO lines |
+| `read_bbox_oriented` | `(width, height, s: str) -> list[str]` | YOLO label lines | Parses 14-column oriented bbox format, outputs YOLO lines (hardcoded class 2) |
+| `rename_images` | `(folder)` | — | Renames files by trimming last 7 chars + replacing extension with .png |
+
+## Internal Logic
+- **convert()**: Iterates image files in source folder, reads corresponding annotation file, calls format-specific reader, copies image and writes YOLO label to destination.
+- **Pascal VOC**: Parses XML `<object>` elements, maps class names via `name_class_map` (Truck→1, Car/Taxi→2), filters forbidden classes (Motorcycle). Default class = 1.
+- **Oriented bbox**: 14-column space-separated format, extracts min/max from columns 6–13, hardcodes class to 2.
+- **Validation**: Skips labels where normalized coordinates exceed 1.0 (out of bounds).
+
+## Dependencies
+- `cv2` (external) — image reading for dimensions
+- `xml.etree.cElementTree` (stdlib) — Pascal VOC XML parsing
+- `os`, `shutil`, `pathlib` (stdlib)
+
+## Consumers
+None (standalone script).
+
+## Data Models
+None.
+
+## Configuration
+Hardcoded class mappings: `name_class_map = {'Truck': 1, 'Car': 2, 'Taxi': 2}`, `forbidden_classes = ['Motorcycle']`.
+
+## External Integrations
+Filesystem I/O only.
+
+## Security
+None.
+
+## Tests
+None.