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/annotation_queue_handler.md

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+# Module: annotation-queue/annotation_queue_handler
+
+## Purpose
+Async consumer for the Azaion annotation queue (RabbitMQ Streams). Listens for annotation CRUD events and writes/moves image+label files on the filesystem.
+
+## Public Interface
+
+### AnnotationQueueHandler
+| Method | Signature | Returns | Description |
+|--------|-----------|---------|-------------|
+| `__init__` | `()` | — | Reads config.yaml, creates directories, initializes rstream Consumer, reads offset |
+| `start` | `async ()` | — | Starts consumer, subscribes to queue stream, runs event loop |
+| `on_message` | `(message: AMQPMessage, context: MessageContext)` | — | Message callback: routes by AnnotationStatus to save/validate/delete |
+| `save_annotation` | `(ann: AnnotationMessage)` | — | Writes label file + image to data or seed directory based on role |
+| `validate` | `(msg: AnnotationBulkMessage)` | — | Moves annotations from seed to data directory |
+| `delete` | `(msg: AnnotationBulkMessage)` | — | Moves annotations to deleted directory |
+
+### AnnotationQueueHandler.AnnotationName (inner class)
+Helper that pre-computes file paths for an annotation name across data/seed directories.
+
+## Internal Logic
+- **Queue protocol**: Subscribes to a RabbitMQ Streams queue using rstream library with AMQP message decoding. Resumes from a persisted offset stored in `offset.yaml`.
+- **Message routing** (via `application_properties['AnnotationStatus']`):
+  - `Created` / `Edited` → `save_annotation`: If validator role, writes to data dir; else writes to seed dir. For Created status, also saves the image bytes. For Edited by validator, moves image from seed to data.
+  - `Validated` → `validate`: Bulk-moves all named annotations from seed to data directory.
+  - `Deleted` → `delete`: Bulk-moves all named annotations to the deleted directory.
+- **Offset tracking**: After each message, increments offset and persists to `offset.yaml`.
+- **Directory layout**:
+  - `{root}/data/images/` + `{root}/data/labels/` — validated annotations
+  - `{root}/data-seed/images/` + `{root}/data-seed/labels/` — unvalidated annotations
+  - `{root}/data_deleted/images/` + `{root}/data_deleted/labels/` — soft-deleted annotations
+- **Logging**: TimedRotatingFileHandler with daily rotation, 7-day retention, logs to `logs/` directory.
+
+## Dependencies
+- `annotation_queue_dto` — AnnotationStatus, AnnotationMessage, AnnotationBulkMessage
+- `rstream` (external) — RabbitMQ Streams consumer
+- `yaml` (external) — config and offset persistence
+- `asyncio`, `os`, `shutil`, `sys`, `logging`, `datetime` (stdlib)
+
+## Consumers
+None (entry point — runs via `__main__`).
+
+## Data Models
+Uses AnnotationMessage, AnnotationBulkMessage from annotation_queue_dto.
+
+## Configuration
+- `config.yaml`: API creds (url, email, password), queue config (host, port, consumer_user, consumer_pw, name), directory structure (root, data, data_seed, data_processed, data_deleted, images, labels)
+- `offset.yaml`: persisted queue consumer offset
+
+## External Integrations
+- RabbitMQ Streams queue (rstream library) on host `188.245.120.247:5552`
+- Filesystem: `/azaion/data/`, `/azaion/data-seed/`, `/azaion/data_deleted/`
+
+## Security
+- Queue credentials in `config.yaml` (hardcoded — security concern)
+- No encryption of annotation data at rest
+
+## Tests
+None.