Handle concept access

[cpfiffer]

                              // TODO add a concepts column

https://github.com/mind-co/comind-flutter/blob/871116b5b7cc2c4b1036b6d04486f4ca7e3154e4/lib/main.dart#L253

[cpfiffer]

The concept column exists now but has nothing in it, partly because there's no concepts to show. This needs work upstream on the server side.

[cpfiffer]

I'm playing with having the concepts accessible with the hashtag button here on the bottom right of the think bar:

[cpfiffer]

It's still probably a good idea to have this in a more accessible format, i.e. an information-dense column or something.

[cpfiffer]

Current status: the concept button is the # symbol. You are taken to a new window that looks like this:

The remaining part here is to make each concept cart clickable, which will

1. Move the card into your top of mind
2. Pull in a bunch of thoughts related to that concept/generate some language model summaries of the concept