feat(loan-products): wire GL mapping, checker diff view, and approval flow for loan interest rate register

- Add GL account picker (gl-picker.component.ts) for mapping each product row to a GL account
- Extract shared diff logic into rate-register-diff.util.ts + loan-rate-register-diff.util.ts
- Add rate-register-diff component to render before/after changes for checker approval
- Rewire checker-inbox and view-checker-inbox to show loan interest rate register diffs
- Refactor rate-register.service.ts (mock-to-real HTTP wiring, GL-aware payload mapping)
- Simplify preview-register component, moving diff rendering into the shared diff component
- Add glAccountId field to RateChartRow model

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/tasks/loan-rate-register-diff.util.ts

@@ -0,0 +1,169 @@
+/**
+ * Copyright since 2025 Mifos Initiative
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+import { ChangeKind, CommandChange } from './command-diff.util';
+
+/** Entity name the maker-checker queue uses for Loan Base Interest Rate submissions. */
+export const LOAN_BASE_INTEREST_RATE_ENTITY = 'LOANBASEINTERESTRATE';
+
+export function isLoanBaseInterestRateCreate(entityName?: string | null, actionName?: string | null): boolean {
+  return (
+    (entityName ?? '').toUpperCase() === LOAN_BASE_INTEREST_RATE_ENTITY && (actionName ?? '').toUpperCase() === 'CREATE'
+  );
+}
+
+const HEADER_FIELDS: { key: string; label: string }[] = [
+  { key: 'name', label: 'Name' },
+  { key: 'effectiveFromDate', label: 'Effective From Date' },
+  { key: 'currencyCode', label: 'Currency Code' },
+  { key: 'fallbackNoCibilSlab', label: 'Fallback No CIBIL Slab' },
+  { key: 'fallbackBelowMin', label: 'Fallback Below Min' },
+  { key: 'note', label: 'Note' }
+];
+
+const NA = 'N.A.';
+const EMPTY = '—';
+
+/** One chart cell as the checker reads it: a % rate, a formula, or N.A. */
+function cellText(cell: any): string {
+  if (!cell || cell.isNa) {
+    return NA;
+  }
+  if (cell.isFormula && cell.rateFormula) {
+    return String(cell.rateFormula);
+  }
+  return cell.rateValue === null || cell.rateValue === undefined ? NA : `${Number(cell.rateValue)}%`;
+}
+
+function plain(value: any): string {
+  return value === null || value === undefined || value === '' ? EMPTY : String(value);
+}
+
+function kindOf(oldText: string, newText: string, emptyTexts: string[]): ChangeKind {
+  const oldEmpty = emptyTexts.includes(oldText);
+  const newEmpty = emptyTexts.includes(newText);
+  if (oldEmpty && !newEmpty) {
+    return 'ADDED';
+  }
+  if (!oldEmpty && newEmpty) {
+    return 'REMOVED';
+  }
+  return 'MODIFIED';
+}
+
+/**
+ * Compares a submitted Loan Base Interest Rate version against the version currently in force and
+ * returns only the values that differ: header fields, individual rate cells (per loan type and
+ * amount slab) and CIBIL adjustment bands.
+ */
+export function diffLoanRateRegister(submitted: any, active: any): CommandChange[] {
+  const changes: CommandChange[] = [];
+
+  for (const { key, label } of HEADER_FIELDS) {
+    if (submitted?.[key] === undefined) {
+      continue;
+    }
+    const oldText = plain(active?.[key]);
+    const newText = plain(submitted[key]);
+    if (oldText !== newText) {
+      changes.push({ label, kind: kindOf(oldText, newText, [EMPTY]), oldValue: oldText, newValue: newText });
+    }
+  }
+
+  // Rate cells, keyed by loan type + slab order.
+  const cellKey = (c: any) => `${c.productSrNo}|${c.slabOrder}`;
+  const oldCells = new Map<string, any>(
+    (active?.slabs ?? []).map((c: any): [string, any] => [
+      cellKey(c),
+      c
+    ])
+  );
+  const newCells = new Map<string, any>(
+    (submitted?.slabs ?? []).map((c: any): [string, any] => [
+      cellKey(c),
+      c
+    ])
+  );
+  const names = new Map<number, string>();
+  for (const c of active?.slabs ?? []) {
+    if (c.productName) {
+      names.set(c.productSrNo, c.productName);
+    }
+  }
+  for (const p of submitted?.products ?? []) {
+    names.set(p.srNo, p.name);
+  }
+
+  const allKeys = new Set<string>([
+    ...newCells.keys(),
+    ...oldCells.keys()
+  ]);
+  const cellChanges = [...allKeys]
+    .map((k) => {
+      const before = oldCells.get(k);
+      const after = newCells.get(k);
+      const ref = after ?? before;
+      return {
+        srNo: Number(ref.productSrNo),
+        slabOrder: Number(ref.slabOrder),
+        label: `${names.get(ref.productSrNo) ?? `Loan type ${ref.productSrNo}`} — ${ref.slabLabel ?? `Slab ${ref.slabOrder + 1}`}`,
+        oldText: before ? cellText(before) : EMPTY,
+        newText: after ? cellText(after) : EMPTY
+      };
+    })
+    // A cell that is N.A. in the submission and was never in the old version is not a change.
+    .filter((c) => c.oldText !== c.newText && !(c.oldText === EMPTY && c.newText === NA))
+    .sort((a, b) => a.srNo - b.srNo || a.slabOrder - b.slabOrder);
+  for (const c of cellChanges) {
+    changes.push({
+      label: c.label,
+      kind: kindOf(c.oldText, c.newText, [
+        EMPTY,
+        NA
+      ]),
+      oldValue: c.oldText,
+      newValue: c.newText
+    });
+  }
+
+  // CIBIL bands, matched by their score range, so a re-ordered list is not reported as a change.
+  const bandKey = (b: any) => `${b.scoreFrom}-${b.scoreTo}`;
+  const bandText = (b: any) => `${Number(b.adjustmentPct)}% (${b.slabType ?? 'Flat'})`;
+  const oldBands = new Map<string, any>(
+    (active?.cibilSlabs ?? []).map((b: any): [string, any] => [
+      bandKey(b),
+      b
+    ])
+  );
+  const newBands = new Map<string, any>(
+    (submitted?.cibilSlabs ?? []).map((b: any): [string, any] => [
+      bandKey(b),
+      b
+    ])
+  );
+  for (const k of new Set<string>([
+    ...newBands.keys(),
+    ...oldBands.keys()
+  ])) {
+    const before = oldBands.get(k);
+    const after = newBands.get(k);
+    const oldText = before ? bandText(before) : EMPTY;
+    const newText = after ? bandText(after) : EMPTY;
+    if (oldText !== newText) {
+      const ref = after ?? before;
+      changes.push({
+        label: `CIBIL ${ref.scoreFrom}–${ref.scoreTo}${ref.tier ? ` (${ref.tier})` : ''} — Adjustment`,
+        kind: kindOf(oldText, newText, [EMPTY]),
+        oldValue: oldText,
+        newValue: newText
+      });
+    }
+  }
+
+  return changes;
+}