refactor: Style transaction items for untracked accounts

This commit extends the "Untrack Account" feature by applying a special style to transaction items that belong to an untracked account.

- The transaction item template is modified to apply a "dimmed" style to transactions from untracked accounts.
- The styling follows the precedence: Account (untracked) > Category (muted) > Transaction (hidden).
- The dropdown menu for transaction items now shows "Controlled by account" if the transaction's account is untracked.

app/apps/insights/utils/transactions.py

@@ -95,4 +95,6 @@ def get_transactions(request, include_unpaid=True, include_silent=False):
             Q(Q(category__mute=True) & ~Q(category=None)) | Q(mute=True)
         )
 
+    transactions = transactions.exclude(account__in=request.user.untracked_accounts.all())
+
     return transactions