Integrate RabbitMQ for asynchronous OCR Processing on File Uploads

[leonardstruck]

• [x] Define an IQueueService interface with methods like EnqueueAsync, DequeueAsync...
• [x] Implement RabbitMQService as a concrete class that implements the IQueueService
• [x] Create the necessary RabbitMQ infrastructure (exchanges, queues, bindings) as part of the service initialisation.
• [x] Add RabbitMQ configuration settings to appsettings.json
• [x] Dependency Injection: Register the RabbitMQService in the DI container
• [x] Update the file upload endpoint api/documents/post_document to enqueue a message after successful uploads
• [ ] Ensure messages contain all necessary metadata for the OCR worker to process the file.
• [x] Write unit tests for RabbitMQService