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>

agent_service/agents/expenses_agent.py

@@ -13,10 +13,12 @@ from ..tools.expenses_tools import ExpensesTools
 # ---------------------------------------------------------------------------
 
 # Matches an explicitly labeled total line.
-# Handles "Total: $22.46", "GRAND TOTAL 22.46", "Amount Due: 22.46", etc.
+# Handles "Total: $22.46", "GRAND TOTAL 22.46", "Amount Due: 22.46",
+# "Total Sale $58.75" (gas stations), "Net Sale $X", etc.
 _TOTAL_RE = re.compile(
     r'(?:grand\s*total|total\s*due|amount\s*due|balance\s*due|'
-    r'total\s*amount|total\s*charged|you\s*paid|amount\s*paid|total)'
+    r'total\s*amount|total\s*charged|total\s*sale|net\s*sale|'
+    r'sale\s*total|you\s*paid|amount\s*paid|total)'
     r'\s*[:\-]?\s*\$?\s*([\d,]+\.\d{2})',
     re.IGNORECASE,
 )