Compare two Mons in the UI

Need a screen where two mons can be compared by their stats. It should look similar to the current mon view but display two mons and a centralised stat column.

Mon 1 | | Stat | | Mon 2
---|---|---|---|---
60 | = | HP | = | 60
65 | -35 | Attack | +35 | 100
80 | +10 | Defense | -10 | 70
50 | -55 | Speed | +55 | 105
120 | +60 | Special | -60 | 60

The comparison columns should be colored accordingly. Probably show stat gauge on each side too (maybe in a later task?)

This depends on the Dex/Mon data model being updated (#13).

Start by reviewing the current mon view and the Dex/Mon data model update in issue #13. Implement a comparison screen for two mons with a centered stat column, colored comparison values, and the layout shown in the issue; the optional stat gauges can remain a later task.

Written by the indexing model from the issue text.