Standardize author endpoint/table/column names

[fennifith]

"authors" and "profiles" are the same thing, but the names are used interchangably between different endpoints & tables across hoof.

We should consistently use one name across the project - and author aligns with the frontend usage.

Some areas that will need to change:

• All table names in https://github.com/playfulprogramming/hoof/blob/main/packages/db/src/schema/profiles.ts
• The "profiles" and "authors" route files in https://github.com/playfulprogramming/hoof/tree/main/apps/api/src/routes/content should be combined
• Any leftover test names, variable names, columns referencing the above tables, etc.