feat(shares): preview the approval checklist before submit, fix settlement GL option

The Clerk Dashboard's standalone Share Withdrawal Request form never offered a
GL settlement destination -- it always submitted SAVINGS, silently, while the
Cashier's Transaction Entry screen already let a clerk pick any postable GL
account on its CR row. Added the same "Settlement Destination" choice (Savings
/ GL Account) with a searchable GL selector here too, so both entry points to
the same backend endpoint behave the same way.

Both share-withdrawal confirm dialogs (savings settlement and GL settlement, in
transaction-entry.component.ts) now call the backend's new preview-validate
endpoint before showing the confirm dialog, so a clerk sees the same checklist
a manager will see on approval -- a missing GL mapping, an unverified KYC, an
open AML alert -- before committing to the request, not after a manager has
already spent time reviewing it. A failing check is shown, not blocked: real
hard rules are still enforced server-side at approve(). Guarded with a 5s
timeout and a fallback message so a slow or unavailable check can never leave
the dialog looking stuck.

error-handler.interceptor.ts: a document/signature attachment whose row
survives but whose file is missing from the content store now resolves to a
silent 404 (matching the existing image-fetch handling) instead of surfacing a
raw error. Background GET failures (500/501/503) on calls a component already
recovers from (photo, attachment, notes, standing instructions, ...) now
surface as a corner toast instead of a blocking modal that has to be dismissed
-- a write action's failure (POST/PUT/DELETE) still gets the centred,
must-acknowledge dialog, since that is the one thing the user was waiting on.
Also surfaces the backend's real message on a 500 instead of a hardcoded
generic sentence.

Backend counterpart: ClerkShareWithdrawalRequestApiResource (preview-validate
endpoint, shared buildShareWithdrawalChecks()) and
DocumentReadPlatformServiceImpl (missing-file 404) land separately.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/app/cashier/transaction-entry/transaction-entry.component.ts

@@ -11,7 +11,7 @@ import { CommonModule } from '@angular/common';
 import { DomSanitizer, SafeResourceUrl } from '@angular/platform-browser';
 import { FormsModule } from '@angular/forms';
 import { HttpClient, HttpParams } from '@angular/common/http';
-import { catchError, debounceTime, distinctUntilChanged, map } from 'rxjs/operators';
+import { catchError, debounceTime, distinctUntilChanged, map, timeout } from 'rxjs/operators';
 import { forkJoin, of, Subject } from 'rxjs';
 import { MatDialog, MatDialogModule, MAT_DIALOG_DATA, MatDialogRef } from '@angular/material/dialog';
 import { MatIconModule } from '@angular/material/icon';
@@ -3425,6 +3425,7 @@ export class TransactionEntryComponent implements OnInit, OnDestroy {
       meetingDate: shareRow.meetingDate,
       description: shareRow.description || null,
       settlementPaymentTypeId: savingsRow.paymentTypeId,
+      settlementMode: 'SAVINGS',
       settlementRowSnapshot
     };
 
@@ -3455,11 +3456,60 @@ export class TransactionEntryComponent implements OnInit, OnDestroy {
         ? 'Pending Manager approval — redemption, settlement and account closure all post together on approval.'
         : 'Pending Manager approval — redemption and settlement both post together on approval.'
     ];
-    this.showConfirmAlert('info', 'Confirm Share Withdrawal Request', confirmLines, 'Submit for Approval', () =>
+    this.showShareWithdrawalConfirm(payload, confirmLines, () =>
       this.doSubmitShareRedemptionTransfer(payload, shareRow, shares, linkedAcNo)
     );
   }
 
+  /**
+   * Shows the confirm dialog with the same checklist the Manager will see when approving this
+   * request — fetched live from the backend (`previewValidate`) rather than re-implemented here,
+   * so it can never show the clerk something different from what the approver actually sees. A
+   * failing check is shown, not blocked: approve() enforces its own hard rules separately (e.g.
+   * Share Advance Collection applied), this list is advisory so problems surface to whoever can
+   * still fix them, before a manager's time is spent on a request that was always going to fail.
+   */
+  private showShareWithdrawalConfirm(
+    payload: Record<string, unknown>,
+    baseLines: string[],
+    onConfirm: () => void
+  ): void {
+    this.clerkShareWithdrawalService
+      .previewValidate(payload)
+      .pipe(
+        // A request that never resolves (slow network, server busy) must not leave the Submit
+        // button looking dead — the dialog still has to open, just without the checklist.
+        timeout(5000),
+        catchError(() => of({ __previewFailed: true }))
+      )
+      .subscribe((res: any) => {
+        const checks: { label: string; pass: boolean; detail: string }[] = res?.checks ?? [];
+        // A failed call (most likely the backend not yet carrying the /preview-validate endpoint)
+        // says so explicitly rather than just omitting the section — a silently empty checklist
+        // looks identical to "everything passed, nothing to show", which is the one reading this
+        // must never give.
+        const checkLines = res?.__previewFailed ? [
+              '',
+              '⚠ Validation checklist unavailable right now — the request can still be submitted.'
+            ] : checks.length ? [
+                '',
+                'Validation Checks (same as Manager approval):',
+                ...checks.map((c) => `${c.pass ? '✓' : '⚠'} ${c.label}: ${c.detail}`)
+              ] : [];
+        // baseLines ends with a blank line followed by the "Pending Manager approval…" footer
+        // sentence, which must stay last so the modal renders it as a footnote rather than a
+        // key/value row — so the checklist is spliced in just before that pair, not appended after.
+        const footerStart =
+          baseLines.length >= 2 && baseLines[baseLines.length - 2] === '' ? baseLines.length - 2 : baseLines.length;
+        const lines = [
+          ...baseLines.slice(0, footerStart),
+          ...checkLines,
+          ...baseLines.slice(footerStart)
+        ];
+        this.showConfirmAlert('info', 'Confirm Share Withdrawal Request', lines, 'Submit for Approval', onConfirm);
+      });
+  }
+
   /**
    * Share redemption settled to a GL account the clerk picks on the CR row, instead of the
    * member's linked savings account — mirrors submitShareRedemptionTransfer() above, but the
@@ -3571,7 +3621,7 @@ export class TransactionEntryComponent implements OnInit, OnDestroy {
         ? 'Pending Manager approval — redemption, settlement and account closure all post together on approval.'
         : 'Pending Manager approval — redemption and settlement both post together on approval.'
     ];
-    this.showConfirmAlert('info', 'Confirm Share Withdrawal Request', confirmLines, 'Submit for Approval', () =>
+    this.showShareWithdrawalConfirm(payload, confirmLines, () =>
       this.doSubmitShareGlSettlementTransfer(payload, shareRow, shares, glRow.acNo)
     );
   }