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/branch-day/branch-day.component.html

@@ -107,11 +107,26 @@
         </span>
       </div>
       @if (canOperate) {
-        <button type="button" class="pg-btn pg-btn--primary" (click)="startClose(openDay)">
+        <button
+          type="button"
+          class="pg-btn pg-btn--primary"
+          (click)="startClose(openDay)"
+          [disabled]="interestPending.length > 0"
+        >
           <mat-icon>lock</mat-icon> Close Day
         </button>
       }
     </div>
+    @if (interestPending.length > 0) {
+      <div class="bd-interest-alert">
+        <mat-icon>warning</mat-icon>
+        <span>
+          Savings interest posting report is not approved for <strong>{{ interestPending.join(', ') }}</strong
+          >. Approve it in <a routerLink="/reports/interest-posting">Reports → Interest Posting Reports</a> before
+          closing the day.
+        </span>
+      </div>
+    }
   } @else if (loaded && canOperate) {
     <div class="bd-current bd-current--shut">
       <div class="bd-current__main">