style(ui): Harmonize watchlist design - align colors with /web

- Updated background gradient from dark violet to light blue (#1a1a2e0%, #16213e100%)
- Harmonized header design colors and layout to match /web page
- Aligned button styles for consistency
- Kept all watchlist functionality intact

templates/watchlist.html

@@ -178,6 +178,18 @@
             font-size: 12px;
         }
 
+        .header-back-btn {
+            margin-top: 15px;
+        }
+
+        .modal-action-btn {
+            flex: 1;
+            padding: 12px;
+            font-size: 14px;
+            cursor: pointer;
+        }
+
+
         /* Filter tabs at top */
         .watchlist-header-filter {
             margin-top: 20px;
@@ -190,7 +202,7 @@
         <div class="watchlist-header">
             <h1>📋 Ma Watchlist</h1>
             <p>Suivez vos animes préférés et téléchargez automatiquement les nouveaux épisodes</p>
-            <button type="button" class="btn-secondary" onclick="window.location.href = '/web'" style="margin-top: 15px;">
+            <button type="button" class="btn-secondary header-back-btn" onclick="window.location.href = '/web'">
                 ← Retour à l'accueil
             </button>
         </div>
@@ -439,10 +451,10 @@
                             </div>
 
                             <div style="display: flex; gap: 10px; margin-top: 30px;">
-                                <button class="btn-primary" onclick="saveSettings()" style="flex: 1; padding: 12px; border: none; border-radius: 8px; font-size: 14px; cursor: pointer;">
+                                <button class="btn-primary modal-action-btn" onclick="saveSettings()">
                                     💾 Enregistrer
                                 </button>
-                                <button class="btn-secondary" onclick="closeSettingsModal()" style="flex: 1; padding: 12px; background: rgba(255,255,255,0.1); border: 1px solid rgba(255,255,255,0.2); border-radius: 8px; color: #fff; font-size: 14px; cursor: pointer;">
+                                <button class="btn-secondary modal-action-btn" onclick="closeSettingsModal()">
                                     Annuler
                                 </button>
                             </div>