fix(expenses): add 'Total Sale' and 'Net Sale' to labeled-total pattern

Gas station receipts (Costco, Shell, etc.) print "Total Sale $X.XX" — the
word "Sale" between "Total" and the amount prevented _TOTAL_RE from matching,
causing the Costco receipt to fall through to the max-scan heuristic and
return a garbled OCR value instead of the correct total.

Also add "Net Sale" and "Sale Total" variants for broader coverage.
79 tests, all passing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_expenses_agent.py

@@ -473,6 +473,15 @@ class TestExtractAmount:
         text = 'Items  5.00\nTax 0.50\nTotal\n5.50'
         assert _extract_amount_from_text(text) == 5.50
 
+    def test_total_sale_gas_station(self):
+        # Costco / Shell gas receipts say "Total Sale $X.XX", not "Total: $X.XX"
+        text = 'Pump  9  16.189 Gal\nRegular  $ 58.75\nTotal Sale  $ 58.75'
+        assert _extract_amount_from_text(text) == 58.75
+
+    def test_net_sale(self):
+        text = 'Items  22.00\nNet Sale  $22.00'
+        assert _extract_amount_from_text(text) == 22.00
+
     def test_amount_due_with_usd_suffix(self):
         # "Total Charged" is in _TOTAL_RE — Pass 1 catches it
         text = 'Total Charged: $198.40 USD'