feat: add check position selector and fix logo not rendering

Add per-account check position setting (top/middle/bottom/3-per-page)
so checks print in a specific slot on the page. Fix logos never
appearing on checks or in the layout editor — the Logo layout field
was missing from the default seed data and existing accounts.

public/index.html

@@ -472,6 +472,18 @@
           </div>
         </div>
 
+        <p class="settings-section-label">Check Position</p>
+        <div class="form-group">
+          <label for="as-check-position">Print checks in</label>
+          <select id="as-check-position" name="check_position">
+            <option value="3-per-page">All 3 slots (3 per page)</option>
+            <option value="top">Top slot only</option>
+            <option value="middle">Middle slot only</option>
+            <option value="bottom">Bottom slot only</option>
+          </select>
+          <span class="field-hint">Choose which slot(s) on the page to print checks in.</span>
+        </div>
+
         <div id="acct-settings-error" class="wizard-error" hidden></div>
       </form>
     </div>

public/js/app.js

@@ -963,6 +963,7 @@ function openAccountSettings() {
   f.elements.offset_up.value    = a.offset_up    || 0;
   f.elements.offset_down.value  = a.offset_down  || 0;
   document.getElementById('as-second-sig').checked = !!a.second_signature;
+  document.getElementById('as-check-position').value = a.check_position || '3-per-page';
 
   document.getElementById('as-logo').value = '';
   document.getElementById('as-logo-preview').hidden = true;
@@ -1001,6 +1002,7 @@ async function saveAccountSettings() {
     offset_up:      parseFloat(f.elements.offset_up.value)    || 0,
     offset_down:      parseFloat(f.elements.offset_down.value)  || 0,
     second_signature: document.getElementById('as-second-sig').checked ? 1 : 0,
+    check_position:   document.getElementById('as-check-position').value,
     logo_data:        acctSettings.logoData || null,
   };