fix(test): update COLUMN_DEFS-length assertion for on_demand_monthly

#322 (now merged) added the on_demand_monthly column to the recs table,
bringing COLUMN_DEFS.length to 13. The visibility-feature test was
written when the count was 12 — update it post-rebase so the suite
stays green.

Author: cristim

frontend/src/__tests__/recommendations.test.ts

@@ -4182,7 +4182,7 @@ describe('Column visibility (issue #318)', () => {
   // --- TOGGLEABLE_COLUMNS and COLUMN_DEFS ---
 
   describe('COLUMN_DEFS and TOGGLEABLE_COLUMNS', () => {
-    test('COLUMN_DEFS contains all 12 column ids', () => {
+    test('COLUMN_DEFS contains all 13 column ids', () => {
       const keys = COLUMN_DEFS.map((c) => c.key);
       expect(keys).toContain('provider');
       expect(keys).toContain('account');
@@ -4195,8 +4195,9 @@ describe('Column visibility (issue #318)', () => {
       expect(keys).toContain('savings');
       expect(keys).toContain('upfront_cost');
       expect(keys).toContain('monthly_cost');
+      expect(keys).toContain('on_demand_monthly');
       expect(keys).toContain('effective_savings_pct');
-      expect(COLUMN_DEFS.length).toBe(12);
+      expect(COLUMN_DEFS.length).toBe(13);
     });
 
     test('TOGGLEABLE_COLUMNS excludes fixed identity columns', () => {