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.scss

@@ -372,3 +372,30 @@
     color: #d97706;
   }
 }
+
+// Shown under the open day while a savings interest posting report due today is unapproved.
+.bd-interest-alert {
+  display: flex;
+  align-items: flex-start;
+  gap: 8px;
+  margin: 8px 0 12px;
+  padding: 10px 14px;
+  border: 1px solid #f59e0b;
+  border-radius: 8px;
+  background: #fef3c7;
+  color: #92400e;
+  font-size: 13px;
+
+  mat-icon {
+    flex-shrink: 0;
+    font-size: 20px;
+    width: 20px;
+    height: 20px;
+  }
+
+  a {
+    color: inherit;
+    font-weight: 600;
+    text-decoration: underline;
+  }
+}