fix(py): coerce amount to float and message to string in tx projection

Two remaining make parity diffs vs Go:

- amount: non-numeric sheet values like "---" passed through as strings;
  Go's parseFloat silently returns 0.0 for unparseable values. Add
  get_float helper that matches that behaviour.
- message: numeric cell values (e.g. a bank reference in the message
  column) passed through as float64; Go's getVal uses fmt.Sprint and
  always emits a string. Apply get_str to the message field.

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

scripts/match_payments.py

@@ -255,16 +255,25 @@ def fetch_sheet_data(spreadsheet_id: str, credentials_path: str) -> list[dict]:
                 return str(int(v))
             return str(v)
 
+        def get_float(idx):
+            v = get_val(idx)
+            if isinstance(v, (int, float)):
+                return float(v)
+            try:
+                return float(str(v).strip())
+            except (ValueError, TypeError):
+                return 0.0
+
         tx = {
             "date": format_date(get_val(idx_date)),
-            "amount": get_val(idx_amount),
+            "amount": get_float(idx_amount),
             "manual_fix": get_val(idx_manual),
             "person": get_val(idx_person),
             "purpose": get_val(idx_purpose),
             "inferred_amount": get_val(idx_inferred_amount),
             "sender": get_val(idx_sender),
             "vs": get_str(idx_vs),
-            "message": get_val(idx_message),
+            "message": get_str(idx_message),
             "bank_id": get_val(idx_bank_id),
             "sync_id": get_val(idx_sync_id),
         }