Remove plaid initialiser (#317)

* Remove plaid initialiser

The initializer can be safely removed because:
  - Config is lazily loaded via Provider::Registry
  - reload_configuration is called after settings updates
  - All calling code handles nil configs gracefully
  - Initial nil state is fine - config loads on first use

* Fix for missing config

* Actually don't pollute application.rb

* Add currency loading for balances

* Fix race condition on lazy load

* Allow loans to be imported in lunch flow also

* Fix currency processor

lib/tasks/data_migration.rake

@@ -3,6 +3,7 @@ namespace :data_migration do
   # 2025-02-07: EU Plaid items need to be moved over to a new webhook URL so that we can
   # instantiate the correct Plaid client for verification based on which Plaid instance it comes from
   task eu_plaid_webhooks: :environment do
+    Provider::PlaidEuAdapter.ensure_configuration_loaded
     provider = Provider::Plaid.new(Rails.application.config.plaid_eu, region: :eu)
 
     eu_items = PlaidItem.where(plaid_region: "eu")