feat(savings,shares): bidirectional savings/share account linking, new Migrate Cash Denomination screen

- Savings account creation shows a required "Default Share Account" picker once Share Linking is
  enabled, populated from the client's active share accounts; submits shareAccountId alongside it.
- Fixes a real data-loss bug on Share Account creation: the Charges step re-seeded its table from
  the product's default charges on every ngOnChanges firing (e.g. stepping back to Details and
  forward again), silently discarding a charge the clerk had already added, edited, or removed - a
  pristine guard existed for exactly this but wasn't checked in ngOnChanges. Now it is.
- Removes the hard "required" on Share Account creation's Default Savings Account field, matching
  the backend now accepting a share account with no linked savings account.
- New /accounting/migrate-cash-denomination screen: counts a branch's opening cash into notes and
  coins, checks it against (or defines, if unset) the Cash GL account's balance, and opens the
  branch's first business day with that same count - the vault-side counterpart to Migrate Opening
  Balances, kept under Accounting rather than Branch Ops/Cashier so it isn't reachable by mistake.

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

src/app/savings/create-savings-account/create-savings-account.component.ts

@@ -146,6 +146,13 @@ export class CreateSavingsAccountComponent {
       });
       return;
     }
+    if (detailsStep.shareLinkingEnabled && !detailsStep.shareAccountId) {
+      this.alertService.alert({
+        type: 'Error',
+        message: 'Share Linking is enabled — please select the share account to link before submitting.'
+      });
+      return;
+    }
     const locale = this.settingsService.language.code;
     const dateFormat = this.settingsService.dateFormat;
     const monthDayFormat = 'dd MMMM';
@@ -208,6 +215,14 @@ export class CreateSavingsAccountComponent {
             type: 'Error',
             message: 'An account with this External ID already exists. Please use a unique External ID.'
           });
+        } else if (
+          errorCode === 'error.msg.savingsaccount.share.account.required' ||
+          errorCode === 'error.msg.savingsaccount.share.account.not.active.for.client'
+        ) {
+          this.alertService.alert({
+            type: 'Error',
+            message: 'Please select an active share account belonging to this client before submitting.'
+          });
         }
       }
     });

src/app/savings/savings-account-stepper/savings-account-details-step/savings-account-details-step.component.html

@@ -126,6 +126,28 @@
             <mat-option [value]="false">No</mat-option>
           </mat-select>
         </mat-form-field>
+
+        @if (shareLinkingEnabled) {
+          <mat-form-field appearance="outline" class="sad-field">
+            <mat-label>Default Share Account</mat-label>
+            <mat-select
+              required
+              [(ngModel)]="shareAccountId"
+              [ngModelOptions]="{ standalone: true }"
+              [disabled]="readOnly"
+            >
+              @for (account of activeShareAccounts; track account.id) {
+                <mat-option [value]="account.id"> {{ account.accountNo }} - {{ account.productName }} </mat-option>
+              }
+            </mat-select>
+            @if (!shareAccountId) {
+              <mat-error>Default Share Account is <strong>required</strong></mat-error>
+            }
+            @if (activeShareAccounts.length === 0) {
+              <mat-hint>This client has no active share account. Open one first, or turn off Share Linking.</mat-hint>
+            }
+          </mat-form-field>
+        }
       </div>
     </div>
 

src/app/savings/savings-account-stepper/savings-account-details-step/savings-account-details-step.component.ts

@@ -78,6 +78,11 @@ export class SavingsAccountDetailsStepComponent implements OnInit {
 
   productTemplate: any = null;
   shareLinkingEnabled = false;
+  /** The client's active share accounts, offered as the "Default Share Account" once Share Linking
+   *  is enabled — the reverse of the "Default Savings Account" picker Share Account creation
+   *  already shows. Fetched once for the client this form is for, since it never changes mid-form. */
+  activeShareAccounts: any[] = [];
+  shareAccountId: number | null = null;
   accountTypeOptions: string[] = [];
   customerSegmentOptions: string[] = [];
   selectedAccountType: string | null = null;
@@ -209,6 +214,10 @@ export class SavingsAccountDetailsStepComponent implements OnInit {
     const clientId = this.savingsAccountTemplate?.clientId;
     if (clientId) {
       this.primaryClientId = clientId;
+      this.savingsService.getClientActiveShareAccounts(clientId).subscribe({
+        next: (accounts) => (this.activeShareAccounts = accounts || []),
+        error: () => (this.activeShareAccounts = [])
+      });
       this.clientsService.getClientData(String(clientId)).subscribe((client: any) => {
         this.primaryClientName = client?.displayName ?? client?.fullname ?? '';
         this.primaryClientCif = client?.cifNumber ?? client?.cifNo ?? '';
@@ -450,6 +459,9 @@ export class SavingsAccountDetailsStepComponent implements OnInit {
     if (ea.shareLinkingEnabled !== undefined) {
       this.shareLinkingEnabled = !!ea.shareLinkingEnabled;
     }
+    if (ea.shareAccountId) {
+      this.shareAccountId = ea.shareAccountId;
+    }
     this.cdr.detectChanges();
   }
 
@@ -669,6 +681,9 @@ export class SavingsAccountDetailsStepComponent implements OnInit {
     }
 
     value.shareLinkingEnabled = this.shareLinkingEnabled;
+    if (this.shareLinkingEnabled && this.shareAccountId) {
+      value.shareAccountId = this.shareAccountId;
+    }
 
     return value;
   }

src/app/savings/savings.service.ts

@@ -181,6 +181,12 @@ export class SavingsService {
     return this.http.get('/savingsaccounts/template', { params: httpParams });
   }
 
+  /** A client's active share accounts — for the "Default Share Account" picker shown once Share
+   *  Linking is enabled on a savings account being created. */
+  getClientActiveShareAccounts(clientId: number): Observable<any[]> {
+    return this.http.get<any[]>(`/clients/${clientId}/activeshareaccounts`);
+  }
+
   /**
    * @param {any} savingsAccount Savings Account
    * @returns {Observable<any>}