feat(shares,tasks): centralized Additional Shares approval queue, remove unused Share Savings Debit

- Add Approval Center tab "Share Addition Requests": lists every pending additional-share tranche
  across all accounts (backed by the new /v1/shareadditionrequests endpoint), with a detail popup
  showing the board resolution and the route-specific proof of funding (voucher(s) for cash, or the
  linked savings account for savings). Approve/Reject call the same native
  approveadditionalshares/rejectadditionalshares commands the account-page buttons already used.
- Remove "Debit from Savings" dialog/button and the "Share Savings Debit" Checker Inbox tab -- zero
  rows ever recorded on either tenant since it was built.
- Remove "Approve Additional Shares"/"Reject Additional Shares" from the account-page menu now that
  every tranche is reviewed from the centralized queue instead.
- Harden SharesButtonsConfiguration.removeButton(): a not-found name fed to splice(-1, 1) was quietly
  deleting the LAST button in the array instead of doing nothing -- removing the two menu entries
  above would otherwise have silently broken the rest of the Active-account button bar.

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

src/app/tasks/tasks-routing.module.ts

@@ -19,7 +19,7 @@ import { CheckerInboxComponent } from './checker-inbox-and-tasks-tabs/checker-in
 import { WithdrawalRequestsComponent } from './checker-inbox-and-tasks-tabs/withdrawal-requests/withdrawal-requests.component';
 import { ShareWithdrawalRequestsComponent } from './checker-inbox-and-tasks-tabs/share-withdrawal-requests/share-withdrawal-requests.component';
 import { DividendRequestsComponent } from './checker-inbox-and-tasks-tabs/dividend-requests/dividend-requests.component';
-import { ShareSavingsDebitRequestsComponent } from './checker-inbox-and-tasks-tabs/share-savings-debit-requests/share-savings-debit-requests.component';
+import { ShareAdditionRequestsComponent } from './checker-inbox-and-tasks-tabs/share-addition-requests/share-addition-requests.component';
 import { DepositRequestsComponent } from './checker-inbox-and-tasks-tabs/deposit-requests/deposit-requests.component';
 import { DisbursementRequestsComponent } from './checker-inbox-and-tasks-tabs/disbursement-requests/disbursement-requests.component';
 import { ClientApprovalComponent } from './checker-inbox-and-tasks-tabs/client-approval/client-approval.component';
@@ -183,9 +183,9 @@ const routes: Routes = [
           data: { title: 'Dividend Requests' }
         },
         {
-          path: 'share-savings-debit-requests',
-          component: ShareSavingsDebitRequestsComponent,
-          data: { title: 'Share Savings Debit Requests' }
+          path: 'share-addition-requests',
+          component: ShareAdditionRequestsComponent,
+          data: { title: 'Share Addition Requests' }
         },
         {
           path: 'deposit-requests',