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/components/08_annotation_queue/description.md

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+# Component: Annotation Queue Service
+
+## Overview
+Self-contained async service that consumes annotation CRUD events from a RabbitMQ Streams queue and persists images + labels to the filesystem. Operates independently from the training pipeline.
+
+**Pattern**: Message-driven event handler / consumer service
+**Upstream**: External RabbitMQ Streams queue (Azaion platform)
+**Downstream**: Data Pipeline (files written become input for augmentation)
+
+## Modules
+- `annotation-queue/annotation_queue_dto` — message DTOs (AnnotationMessage, AnnotationBulkMessage, AnnotationStatus, Detection, etc.)
+- `annotation-queue/annotation_queue_handler` — async queue consumer with message routing and file management
+
+## Internal Interfaces
+
+### AnnotationQueueHandler
+```python
+AnnotationQueueHandler()
+AnnotationQueueHandler.start() -> async
+AnnotationQueueHandler.on_message(message: AMQPMessage, context: MessageContext) -> None
+AnnotationQueueHandler.save_annotation(ann: AnnotationMessage) -> None
+AnnotationQueueHandler.validate(msg: AnnotationBulkMessage) -> None
+AnnotationQueueHandler.delete(msg: AnnotationBulkMessage) -> None
+```
+
+### Key DTOs
+```python
+AnnotationMessage(msgpack_bytes)  # Full annotation with image + detections
+AnnotationBulkMessage(msgpack_bytes)  # Bulk validate/delete
+AnnotationStatus: Created(10), Edited(20), Validated(30), Deleted(40)
+RoleEnum: Operator(10), Validator(20), CompanionPC(30), Admin(40), ApiAdmin(1000)
+```
+
+## Data Access Patterns
+- **Queue**: Consumes from RabbitMQ Streams queue `azaion-annotations` using rstream library
+- **Offset persistence**: `offset.yaml` tracks last processed message offset for resume
+- **Filesystem writes**:
+  - Validated annotations → `{root}/data/images/` + `{root}/data/labels/`
+  - Unvalidated (seed) → `{root}/data-seed/images/` + `{root}/data-seed/labels/`
+  - Deleted → `{root}/data_deleted/images/` + `{root}/data_deleted/labels/`
+
+## Implementation Details
+- **Message routing**: Based on `AnnotationStatus` from AMQP application properties:
+  - Created/Edited → save label + optionally image; validator role writes to data, operator to seed
+  - Validated (bulk) → move from seed to data
+  - Deleted (bulk) → move to deleted directory
+- **Role-based logic**: `RoleEnum.is_validator()` returns True for Validator, Admin, ApiAdmin — these roles write directly to validated data directory
+- **Serialization**: Messages are msgpack-encoded with positional integer keys. Detections are embedded as a JSON string within the msgpack payload.
+- **Offset tracking**: After each successfully processed message, offset is persisted to `offset.yaml` (survives restarts)
+- **Logging**: TimedRotatingFileHandler with daily rotation, 7-day retention, writes to `logs/` directory
+- **Separate dependencies**: Own `requirements.txt` (pyyaml, msgpack, rstream only)
+- **Own config.yaml**: Points to test directories by default (`data-test`, `data-test-seed`)
+
+## Caveats
+- Credentials hardcoded in `config.yaml` (queue host, user, password)
+- AnnotationClass duplicated (third copy) with slight differences from dto/ version
+- No reconnection logic for queue disconnections
+- No dead-letter queue or message retry on processing failures
+- `save_annotation` writes empty label files when detections list has no newline separators between entries
+- The annotation-queue `config.yaml` uses different directory names (`data-test` vs `data`) than the main `config.yaml` — likely a test vs production configuration issue
+
+## Dependency Graph
+```mermaid
+graph TD
+    annotation_queue_dto --> annotation_queue_handler
+    rstream_ext[rstream library] --> annotation_queue_handler
+    msgpack_ext[msgpack library] --> annotation_queue_dto
+```
+
+## Logging Strategy
+`logging` module with TimedRotatingFileHandler. Format: `HH:MM:SS|message`. Daily rotation, 7-day retention. Also outputs to stdout.