Add blank workbook template, example rules file, and Create blank workbook button

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

statement_loader.py

@@ -418,7 +418,7 @@ def apply(new_rows, workbook=WORKBOOK):
                 lo[a] = min(lo.get(a, d), d); hi[a] = max(hi.get(a, d), d)
     for rr in range(1, rc.max_row + 1):
         a = rc.cell(rr, 1).value
-        if a in lo and rc.cell(rr, 2).value and "–" in str(rc.cell(rr, 2).value):
+        if a in lo and rc.cell(rr, 2).value and ("–" in str(rc.cell(rr, 2).value) or str(rc.cell(rr, 2).value) == "no data yet"):
             rc.cell(rr, 2).value = f"{lo[a]:%-m/%-d/%Y} – {hi[a]:%-m/%-d/%Y}"
     # Review Items
     if added_payees or any(r.needs_review for r in log_rows):