fix(sync): dashboard sync covers current year plus Nov-Dec of previous

/sync-bank now uses one shared default window in both implementations:
1 November of the previous year to 31 December of the current year.
Payments dated around New Year are picked up in January; duplicates
are still filtered by Sync ID.

Python used a hardcoded 2026 window and would have stopped syncing on
2027-01-01; Go used the current calendar year only.

Adds make sync-year [YEAR=N] with the same window. The CLI default
without flags (last 30 days) is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

legacy/app.py

@@ -30,7 +30,7 @@ from views import (
     adapt_junior_members,
 )
 from cache_utils import get_sheet_modified_time, read_cache, write_cache, _LAST_CHECKED, flush_cache
-from sync_fio_to_sheets import sync_to_sheets
+from sync_fio_to_sheets import sync_to_sheets, default_sync_window
 from infer_payments import infer_payments
 
 def get_cached_data(cache_key, sheet_id, fetch_func, *args, serialize=None, deserialize=None, **kwargs):
@@ -128,13 +128,14 @@ def sync_bank():
     success = True
     try:
         with contextlib.redirect_stdout(output), contextlib.redirect_stderr(output):
-            # sync_to_sheets: equivalent of make sync-2026
-            output.write("=== Syncing Fio transactions (2026) ===\n")
+            # sync_to_sheets: equivalent of make sync-year (same default window as Go)
+            date_from, date_to = default_sync_window()
+            output.write(f"=== Syncing Fio transactions ({date_from} to {date_to}) ===\n")
             sync_to_sheets(
                 spreadsheet_id=PAYMENTS_SHEET_ID,
                 credentials_path=CREDENTIALS_PATH,
-                date_from_str="2026-01-01",
-                date_to_str="2026-12-31",
+                date_from_str=date_from,
+                date_to_str=date_to,
                 sort_by_date=True,
             )
             output.write("\n=== Inferring payment details ===\n")

legacy/scripts/sync_fio_to_sheets.py

@@ -59,6 +59,18 @@ def get_sheets_service(credentials_path: str):
     return _SHEETS_SERVICE
 
 
+def default_sync_window(today=None) -> tuple[str, str]:
+    """Window used by the dashboard sync, as (from, to) in YYYY-MM-DD.
+
+    The whole current calendar year plus the last two months of the previous
+    one, so payments dated around New Year are still picked up in January.
+    Re-fetching is safe because rows are deduplicated by Sync ID.
+    Mirrors DefaultWindow in go/internal/services/banksync/sync.go.
+    """
+    year = (today or datetime.now()).year
+    return f"{year - 1}-11-01", f"{year}-12-31"
+
+
 def as_text_cell(value) -> str:
     """Mark a value to be stored as text when written with USER_ENTERED.
 

legacy/tests/test_app.py

@@ -23,6 +23,20 @@ class TestWebApp(unittest.TestCase):
         app.config['TESTING'] = True
         self.client = app.test_client()
 
+    @patch('app.flush_cache', return_value=0)
+    @patch('app.infer_payments')
+    @patch('app.sync_to_sheets')
+    def test_sync_bank_uses_default_window(self, mock_sync, mock_infer, mock_flush):
+        """/sync-bank syncs the current year plus Nov-Dec of the previous one, not a hardcoded year."""
+        from datetime import datetime
+        year = datetime.now().year
+        response = self.client.get('/sync-bank')
+        self.assertEqual(response.status_code, 200)
+        kwargs = mock_sync.call_args.kwargs
+        self.assertEqual(kwargs['date_from_str'], f"{year - 1}-11-01")
+        self.assertEqual(kwargs['date_to_str'], f"{year}-12-31")
+        mock_infer.assert_called_once()
+
     def test_index_page(self):
         """Test that / returns the refresh meta tag"""
         response = self.client.get('/')

legacy/tests/test_sync_fio.py

@@ -1,9 +1,17 @@
 import contextlib
 import io
 import unittest
+from datetime import datetime
 from unittest.mock import MagicMock, patch
 
-from scripts.sync_fio_to_sheets import COLUMN_LABELS, as_text_cell, sync_to_sheets
+from scripts.sync_fio_to_sheets import COLUMN_LABELS, as_text_cell, default_sync_window, sync_to_sheets
+
+
+class TestDefaultSyncWindow(unittest.TestCase):
+    def test_current_year_plus_last_two_months_of_previous(self):
+        self.assertEqual(default_sync_window(datetime(2026, 10, 8)), ("2025-11-01", "2026-12-31"))
+        self.assertEqual(default_sync_window(datetime(2027, 1, 1)), ("2026-11-01", "2027-12-31"))
+        self.assertEqual(default_sync_window(datetime(2027, 12, 31)), ("2026-11-01", "2027-12-31"))
 
 
 class TestAsTextCell(unittest.TestCase):