Typo Plus Jakarta Sans + renommage libreDecision + mode démo prod + seed mandats

- Fonte : Nunito → Plus Jakarta Sans (moderne, ronde sans être toy)
- Logo : ğ(Decision) → libreDecision (libre italic/muted + Decision bold)
- Footer et watermark DocumentPreview mis à jour
- Mode démo : DEMO_MODE flag dans config.py + auth.py (profils rapides en prod)
- docker-compose : ENVIRONMENT=production explicite + DEMO_MODE=true par défaut
- Seed : +décision Licence G1 v0.4.0, +3 mandats (ComTech, Admin Forgerons, Modération)
  runner 7→10 étapes, import Mandate/MandateStep ajouté

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

frontend/app/app.vue

@@ -108,7 +108,7 @@ function isActive(to: string) {
                 <UIcon name="i-lucide-gavel" class="app-header__logo-icon" />
               </span>
               <span class="app-header__logo-text">
-                <span class="app-header__logo-g">ğ</span><span class="app-header__logo-paren">(</span><span class="app-header__logo-word">Decision</span><span class="app-header__logo-paren">)</span>
+                <span class="app-header__logo-libre">libre</span><span class="app-header__logo-decision">Decision</span>
               </span>
             </NuxtLink>
           </div>
@@ -262,7 +262,7 @@ function isActive(to: string) {
 
       <!-- Footer -->
       <footer class="app-footer">
-        <span>ğ(Decision) v0.1.0</span>
+        <span>libreDecision v0.1.0</span>
         <span class="app-footer__sep">·</span>
         <span>Licence libre</span>
       </footer>
@@ -361,24 +361,17 @@ function isActive(to: string) {
   display: flex;
   align-items: baseline;
   gap: 0;
+  letter-spacing: -0.01em;
 }
 
-.app-header__logo-g {
-  font-size: 1.5rem;
-  font-weight: 800;
-  color: var(--mood-accent);
-  line-height: 1;
+.app-header__logo-libre {
+  font-size: 1.0625rem;
+  font-weight: 400;
   font-style: italic;
-}
-
-.app-header__logo-paren {
-  font-size: 1.125rem;
-  font-weight: 300;
   color: var(--mood-text-muted);
-  opacity: 0.5;
 }
 
-.app-header__logo-word {
+.app-header__logo-decision {
   font-size: 1.125rem;
   font-weight: 700;
   color: var(--mood-text);