feat(clerk): add row add/delete buttons for multi-entry transactions

Clerk can now add multiple rows to enter both CR and DR sides of a
GL-to-account transaction. Add button in footer appends a new row;
each row shows a × delete button when more than one row exists.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -88,6 +88,16 @@
         @for (row of rows; track $index; let i = $index) {
           <div class="ws-card" [class.ws-card--active]="selectedRow === row" (click)="onRowSelect(row, i)">
             <div class="ws-card__badge">{{ i + 1 }}</div>
+            @if (isClerk && rows.length > 1) {
+              <button
+                class="ws-card__del"
+                type="button"
+                (click)="$event.stopPropagation(); deleteRow(i)"
+                title="Remove this row"
+              >
+                ×
+              </button>
+            }
 
             <div class="ws-card__body">
               <!-- ── Row 1: Classification | Account ── -->
@@ -1375,6 +1385,15 @@
               <button class="ws-btn ws-btn--ghost" type="button">Drop</button>
               <button class="ws-btn ws-btn--ghost" type="button" (click)="onSearch()">Search</button>
               <button class="ws-btn ws-btn--mode" type="button">Change Tr.Mode</button>
+              @if (isClerk) {
+                <button class="ws-btn ws-btn--add" type="button" (click)="addRow()" title="Add another transaction row">
+                  <svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5">
+                    <line x1="12" y1="5" x2="12" y2="19" />
+                    <line x1="5" y1="12" x2="19" y2="12" />
+                  </svg>
+                  Add
+                </button>
+              }
             </div>
             <div class="ws-footer__actions">
               <button