Plaid sync domain improvements (#2267)

Breaks our Plaid sync process out into more manageable classes. Notably, this moves the sync process to a distinct, 2-step flow:

1. Import stage - we first make API calls and import Plaid data to "mirror" tables
2. Processing stage - read the raw data, apply business rules, build internal domain models and sync balances

This provides several benefits:

- Plaid syncs can now be "replayed" without fetching API data again
- Mirror tables provide better audit and debugging capabilities
- Eliminates the "all or nothing" sync behavior that is currently in place, which is brittle

app/models/family/auto_categorizer.rb

@@ -70,8 +70,7 @@ class Family::AutoCategorizer
           amount: transaction.entry.amount.abs,
           classification: transaction.entry.classification,
           description: transaction.entry.name,
-          merchant: transaction.merchant&.name,
-          hint: transaction.plaid_category_detailed
+          merchant: transaction.merchant&.name
         }
       end
     end