feat(clients): draw-signature option for Specimen Signature, drop its webcam capture

DrawSignatureDialogComponent (a mouse/touchpad signature pad) already
existed and was used from the client profile view, but wasn't wired into
the KYC step used during client creation/edit — a stale comment there
even referred to a "draw-pad" option as if it were already present.
Wired it in as a third capture method alongside Choose & Crop, then
removed Use Webcam from the signature box specifically (kept for Client
Photograph) per follow-up feedback — a signature is drawn or scanned, not
photographed.

Refactored the file-picker/webcam/draw-pad paths' duplicated stage+upload
logic into shared applySignatureFile()/uploadSignatureFile() helpers.

src/app/clients/client-stepper/client-kyc-step/client-kyc-step.component.html

@@ -1481,8 +1481,8 @@
               <input type="file" accept="image/*" hidden (change)="onSignatureSelected($event)" />
               <fa-icon icon="crop"></fa-icon> Choose &amp; Crop
             </label>
-            <button type="button" class="upload-box__btn upload-box__btn--secondary" (click)="captureWebcamSignature()">
-              <fa-icon icon="video"></fa-icon> Use Webcam
+            <button type="button" class="upload-box__btn upload-box__btn--secondary" (click)="drawSignature()">
+              <fa-icon icon="pen"></fa-icon> Draw Signature
             </button>
           </div>
           @if (photoSigTouched) {