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

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

loader_rules.example.json

@@ -0,0 +1,5 @@
+{
+  "own_names": ["JANE DOE"],
+  "own_bank_hints": ["MY CREDIT UNION"],
+  "csv_accounts": {"1234": "Capital One Card"}
+}