account: fix duplicate billing line + always show badge for founding members

Duplicate "Lifetime · Never billed again" was caused by
insertAdjacentHTML('afterend') appending another <p> on every
renderPlanCard call - and renderPlanCard runs both in init() and on
the onAuthStateChange INITIAL_SESSION event, so the line stacks.
Replaced with a dedicated #plan-billing-note-el container that
setHtml() replaces in place.

Badge: collapsed the two-branch fetch into one path. Founding
members now always see the badge; if member_number is set we render
"#N", otherwise we fall through to "Your number awaits" via the
existing n=0 endpoint behaviour.

src/account.el

@@ -718,6 +718,7 @@ fn account_page(supabase_url: String, supabase_anon_key: String) -> String {
             <div>
               <p class=\"plan-name\" id=\"plan-name-el\">Loading...</p>
               <div id=\"plan-status-el\"></div>
+              <div id=\"plan-billing-note-el\"></div>
             </div>
           </div>
           <div class=\"plan-meta\" id=\"plan-meta-el\"></div>
@@ -1029,7 +1030,7 @@ fn account_page(supabase_url: String, supabase_anon_key: String) -> String {
     }
     setHtml('plan-status-el', statusHtml);
 
-    // Billing note below status
+    // Billing note (replaces, never appends - this function may run more than once on auth state changes)
     var billingNote = '';
     if (plan === 'founding') {
       billingNote = '<p class=\"plan-billing-note\">Lifetime &middot; Never billed again</p>';
@@ -1038,8 +1039,7 @@ fn account_page(supabase_url: String, supabase_anon_key: String) -> String {
     } else {
       billingNote = '<p class=\"plan-billing-note\">On the waitlist</p>';
     }
-    var statusEl = document.getElementById('plan-status-el');
+    setHtml('plan-billing-note-el', billingNote);
-    if (statusEl) statusEl.insertAdjacentHTML('afterend', billingNote);
 
     // Meta
     var meta = '';
@@ -1055,31 +1055,16 @@ fn account_page(supabase_url: String, supabase_anon_key: String) -> String {
       setHtml('plan-meta-el', meta);
     }
 
-    // Founding badge
+    // Founding badge - always show for founding members, with member number if assigned
-    if (plan === 'founding' && memberNum) {
+    if (plan === 'founding') {
       var badgeSection = document.getElementById('badge-section');
       var badgeContainer = document.getElementById('badge-html-container');
-      if (badgeSection && badgeContainer) {
-        badgeSection.style.display = '';
-        // Fetch badge HTML from server
-        fetch('/api/founding-badge?n=' + memberNum)
-          .then(function(r) { return r.text(); })
-          .then(function(html) {
-            badgeContainer.innerHTML = html;
-          })
-          .catch(function(e) {
-            console.error('Failed to load badge:', e);
-          });
-      }
-    } else if (plan === 'founding') {
-      // Founding member but number not yet assigned
-      var badgeSection = document.getElementById('badge-section');
       if (badgeSection) badgeSection.style.display = '';
-      fetch('/api/founding-badge?n=0')
+      var badgeN = memberNum || 0;
+      fetch('/api/founding-badge?n=' + badgeN)
         .then(function(r) { return r.text(); })
         .then(function(html) {
-          var c = document.getElementById('badge-html-container');
+          if (badgeContainer) badgeContainer.innerHTML = html;
-          if (c) c.innerHTML = html;
         })
         .catch(function() {});
     }