Feature: 100 Gründer-Challenge — Leaderboard, Ranking, founder_number

- users.founder_number: sequentielle Nummer #1-#100 (bei Registrierung mit Code oder Admin-Grant)
- Globaler Cap: max. 100 Gründer über alle Partner-Codes zusammen
- GET /api/partner/founders/stats: öffentlich — Slots, Partner-Ranking nach uses, Gründer-Galerie
- Öffentliche Seite /gruender: Fortschrittsbalken, Partner-Challenge-Leaderboard (🥇🥈🥉), Gründer-Grid
- Forum: "Gründer #42"-Badge (lila) neben Autorenname bei Threads + Antworten
- Settings: Badge zeigt "Gründer #N" statt nur "Gründer", klickbar zur /gruender-Seite
- Sidebar: "🏆 100 Gründer"-Link im Footer
- Admin-Grant: Vergabe von founder_number beim manuellen is_founder=1-Setzen
- SW by-v516, APP_VER 493

backend/static/js/pages/forum.js

@@ -392,6 +392,7 @@ window.Page_forum = (() => {
         <div class="forum-thread-author-row">
           <div class="forum-avatar">${_esc(_initial(thread.autor_name))}</div>
           <span style="font-size:0.85rem;color:var(--c-text-secondary)">${_esc(thread.autor_name || 'Unbekannt')}</span>
+          ${thread.autor_founder_number ? `<span style="font-size:10px;font-weight:700;background:#7c3aed;color:#fff;padding:1px 5px;border-radius:4px">Gründer #${thread.autor_founder_number}</span>` : ''}
           <div style="margin-left:auto;display:flex;gap:var(--space-2);align-items:center">
             <button class="${likeClass}" id="thread-like-btn" data-count="${thread.likes || 0}">
               ${UI.icon('heart')} <span id="thread-like-count">${thread.likes || 0}</span>
@@ -589,6 +590,7 @@ window.Page_forum = (() => {
         <div class="forum-post-header">
           <div class="forum-avatar forum-avatar--sm">${_esc(_initial(p.autor_name))}</div>
           <span class="forum-post-author">${_esc(p.autor_name || 'Unbekannt')}</span>
+          ${p.autor_founder_number ? `<span style="font-size:10px;font-weight:700;background:#7c3aed;color:#fff;padding:1px 5px;border-radius:4px">Gründer #${p.autor_founder_number}</span>` : ''}
           <span class="forum-post-date">${_fmtDate(p.created_at)}</span>
         </div>
         <div class="forum-post-body">