feat(rbi-reserve,savings): Form 1/Form 9 returns UI, branch-wise interest posting reports and summary

- Reports > Interest Posting Reports: per branch and product, generate/regenerate
  at any time, approve; branch column, HO-on-behalf marker, posted txn per account
- Reports > Interest Posting Summary (branch-wise) for the head office, with Excel export
- Day Close warns and disables Close Day while the branch's interest report is unapproved
- Savings product accounting: Interest On Savings (expense), Savings Interest Payable
  and Paid (liability rows, required)
- RBI Form 1 statutory and Form 9 return screens, reserve config updates
- Interest posting report GETs exempted from the response cache

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/app/cashier/cashier.service.ts

@@ -205,6 +205,23 @@ export class CashierService {
     return this.http.get('/branchday', { params });
   }
 
+  /**
+   * The savings products whose interest posting report is due for the date and not yet approved —
+   * the backend refuses to close any branch's day while one is pending.
+   */
+  interestDayCloseCheck(
+    date?: string,
+    officeId?: number
+  ): Observable<{ businessDate: string; canClose: boolean; pendingProducts: string[] }> {
+    let params = new HttpParams();
+    if (date) params = params.set('date', date);
+    if (officeId) params = params.set('officeId', String(officeId));
+    return this.http.get<{ businessDate: string; canClose: boolean; pendingProducts: string[] }>(
+      '/savingsinterestpostingreports/day-close-check',
+      { params }
+    );
+  }
+
   /** Days opened and never closed — today's own open day excluded. */
   branchDayMissed(officeId?: number): Observable<any> {
     let params = new HttpParams();