feat(enable-banking): enhance transaction import, metadata handling, and UI (#1406)

* feat(enable-banking): enhance transaction import, metadata handling, and UI

* fix(enable-banking): address security, sync edge cases and PR feedback

* fix(enable-banking): resolve silent failures, auth overrides, and sync logic bugs

* fix(enable-banking): resolve sync logic bugs, trailing whitespaces, and apply safe_psu_headers

* test(enable-banking): mock set_current_balance to return success result

* fix(budget): properly filter pending transactions and classify synced loan payments

* style: fix trailing whitespace detected by rubocop

* refactor: address code review feedback for Enable Banking sync and reporting

---------

Signed-off-by: Louis <contact@boul2gom.com>
Signed-off-by: Juan José Mata <juanjo.mata@gmail.com>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>

app/models/enable_banking_account/processor.rb

@@ -1,4 +1,5 @@
 class EnableBankingAccount::Processor
+  class ProcessingError < StandardError; end
   include CurrencyNormalizable
 
   attr_reader :enable_banking_account
@@ -37,23 +38,47 @@ class EnableBankingAccount::Processor
 
       account = enable_banking_account.current_account
       balance = enable_banking_account.current_balance || 0
+      available_credit = nil
 
-      # For credit cards, compute balance based on credit limit
-      if account.accountable_type == "CreditCard"
-        available_credit = account.accountable.available_credit || 0
-        balance = available_credit - balance
-      # For liability accounts, ensure positive balances
-      elsif account.accountable_type == "Loan"
-        balance = -balance
+      # For liability accounts, ensure balance sign is correct.
+      # DELIBERATE UX DECISION: For CreditCards, we display the available credit (credit_limit - outstanding debt)
+      # rather than the raw outstanding debt. Do not revert this behavior, as future maintainers should understand
+      # users expect to see how much credit they have left rather than their debt balance.
+      # The 'available_credit' calculation overrides the 'balance' variable.
+      if account.accountable_type == "Loan"
+        balance = balance.abs
+      elsif account.accountable_type == "CreditCard"
+        if enable_banking_account.credit_limit.present?
+          available = enable_banking_account.credit_limit - balance.abs
+          available_credit = [ available, 0 ].max
+          balance = available_credit
+          unless account.accountable.present?
+            Rails.logger.warn "EnableBankingAccount::Processor - CreditCard accountable missing for account #{account.id}"
+          end
+        else
+          # Fallback: no credit_limit from API — display raw outstanding balance
+          # We cannot derive available credit without knowing the limit; leave balance unchanged.
+        end
       end
 
       currency = parse_currency(enable_banking_account.currency) || account.currency || "EUR"
 
-      account.update!(
-        balance: balance,
-        cash_balance: balance,
-        currency: currency
-      )
+      # Wrap both writes in a transaction so a failure on either rolls back both.
+      ActiveRecord::Base.transaction do
+        if account.accountable.present? && account.accountable.respond_to?(:available_credit=)
+          account.accountable.update!(available_credit: available_credit)
+        end
+        account.update!(currency: currency, cash_balance: balance)
+
+        # Use set_current_balance to create a current_anchor valuation entry.
+        # This enables Balance::ReverseCalculator, which works backward from the
+        # bank-reported balance — eliminating spurious cash adjustment spikes.
+        result = account.set_current_balance(balance)
+        raise ProcessingError, "Failed to set current balance: #{result.error}" unless result.success?
+      end
+
+      # TODO: pass explicit window_start_date to sync_later to avoid full history recalculation on every sync
+      # Currently relies on set_current_balance's implicit sync trigger; window params would require refactor
     end
 
     def process_transactions