Fix false positive inactive hints for SimpleFin accounts during chunked imports (#573)

* Add tests and logic for zero balance handling and inactivity detection

- Updated `SimplefinItem::ImporterInactiveTest` to include cases for chunked imports, credit cards, and loans.
- Added logic to skip zero balance detection for liability accounts (e.g., credit cards, loans).
- Ensured zero balance runs are counted only once per sync to avoid false positives during chunked imports.

* Add nil safety

---------

Co-authored-by: Josh Waldrep <joshua.waldrep5+github@gmail.com>

app/models/simplefin_item/importer.rb

@@ -158,6 +158,16 @@ class SimplefinItem::Importer
         return
       end
 
+      # Skip zero balance detection for liability accounts (CreditCard, Loan) where
+      # 0 balance with no holdings is normal (paid off card/loan)
+      account_type = simplefin_account.current_account&.accountable_type
+      return if %w[CreditCard Loan].include?(account_type)
+
+      # Only count each account once per sync run to avoid false positives during
+      # chunked imports (which process the same account multiple times)
+      zero_balance_seen_keys << key if zeroish_balance && no_holdings
+      return if zero_balance_seen_keys.count(key) > 1
+
       if zeroish_balance && no_holdings
         stats["zero_runs"][key] = stats["zero_runs"][key].to_i + 1
         # Cap to avoid unbounded growth
@@ -173,6 +183,11 @@ class SimplefinItem::Importer
       end
     end
 
+    # Track accounts that have been flagged for zero balance in this sync run
+    def zero_balance_seen_keys
+      @zero_balance_seen_keys ||= []
+    end
+
     # Track seen error fingerprints during a single importer run to avoid double counting
     def seen_errors
       @seen_errors ||= Set.new