Implement chunking business logic

[EndlessReform]

Implement the backend functionality that extracts text data from the PostgreSQL database for chunking. This should filter based on crude parameters like post time and upvotes, in addition to using clusters for a more targeted selection.

Tasks:

Query PostgreSQL database to retrieve post text based on criteria.
Apply any preprocessing steps necessary to prepare the text for chunking.

Acceptance Criteria:

Text from 10k-100k posts can be filtered and prepared for chunking.

Depends on #13