Dev test: Switch to using async queries for database

**Describe the task**
Project was started using psycopg, which makes blocking database queries. We need to switch to all queries used by the API to be asynchronous. (Blocking calls can block all other clients that happen to be connected to the same thread!)

**Acceptance Criteria**
- [ ] psycopg is removed
- [ ] all db queries are async

**Additional context**
- All queries need to be re-written to make use of async

The issue names no files or tests. Start by locating the API's psycopg dependency and inventorying every database query; then determine how each query must become asynchronous. Done means psycopg is removed and all database queries used by the API are async.

Written by the indexing model from the issue text.