## Overview
With T809 finished, on blog tag pages, we should retrieve "tagged" posts by their category, not inline hashtags.
## Implementation
Replace the [query](https://github.com/writefreely/writefreely/blob/a122e4e98a1f402f1e999ac30665187ce5d8dc89/database.go#L1229-L1233) that looks up posts by regex, with one that selects `post_id`s from the `post_categories` table.