Sometimes the local index can be in an incorrect state and the only way to fix this right now is to delete the local data and log in again, re-downloading everything. We could just re-index based on the locally stored data and not have to re-download everything.

AC

• There is a button in the Settings that says "Re-Index current email cache"
• There should also be explainer text for what this is doing
• When used, the index is purged and rebuilt from the local cache
• Add loading indicator when indexing is happening.