Implement Personal Message Context

[RealistikDash]

This PR adds keeping track of personal context for queries done outside of threads, alongside the clear_context command.

This aims to make using the query command more viable for usecases where the bot cannot create a thread (such as group chats), allowing for more fluent conversations. The clear_context command was added to make context switching easier, as you dont want the bot bringing up your cooking queries when you want to ask it about code.

Potential issues

• Personal messages are not counted in the monthly cost and even if they were, context clearing would invalidate them. Perhaps use a "deleted" field in the database to account for these.
• Currently, context limits are handled by a constant (last 5 messages), which is pretty small. Perhaps using a time based one (messages from the last hour or so) would be more convenient and adding input token calculations into the fetch query directly (last n tokens until you hit the input token limit for the model) to max out the context.