feat: v6.0.0 PWA offline support

- manifest + icones, service worker (precache, network-first, Background Sync)

- module client FlowOffline (IndexedDB, queue, delta, flush) + hook editeur

- endpoints /api/v2/sync/{delta,batch,status} + moteur de sync (conflits LWW/orpheline/copie offline)

- migrations offline_sync_queue + sync_version (triggers)

- UI offline (banner, badge sync, toasts, icone dirty) + doc /help

- tests pytest (sync, migrations, SW, offline) + E2E Playwright; bump 6.0.0

app/templates/local_workspace.html

@@ -212,7 +212,8 @@
 .modified-dot.show{display:block;}
 
 /* Offline banner */
-.offline-banner{position:fixed;top:0;left:0;right:0;background:var(--danger);color:#fff;text-align:center;padding:6px 12px;font-size:12px;z-index:500;font-weight:500;}
+.offline-banner{position:fixed;top:0;left:0;right:0;background:var(--danger);color:#fff;text-align:center;padding:6px 12px;font-size:12px;z-index:500;font-weight:500;display:flex;align-items:center;justify-content:center;gap:12px;}
+.offline-badge{background:rgba(255,255,255,.22);border-radius:10px;padding:1px 8px;font-size:11px;font-weight:600;}
 
 /* Pinned indicator */
 .pin-icon{font-size:10px;color:var(--text-tertiary);cursor:pointer;margin-left:4px;opacity:0;transition:opacity 150ms;}
@@ -595,6 +596,7 @@ window._wsInitData = (function() {
 
     // Online/offline
     online: navigator.onLine,
+    pendingSyncCount: 0,
     pinnedIds: (function() {
       try { return JSON.parse(localStorage.getItem('fd_ws_pinned') || '[]'); }
       catch(e) { return []; }
@@ -648,6 +650,13 @@ window._wsInitData = (function() {
         var self = this;
         window.addEventListener('online', function() { self.online = true; });
         window.addEventListener('offline', function() { self.online = false; });
+        // v6.0.0 PWA: reflect offline queue state from the client module
+        if (window.FlowOffline && window.FlowOffline.onChange) {
+          window.FlowOffline.onChange(function(s) {
+            self.online = s.online;
+            self.pendingSyncCount = s.pendingSyncCount;
+          });
+        }
         // Side-peek editor posts renames here so the tree/peek title stay in sync.
         window.addEventListener('message', function(ev) {
           if (ev.origin !== window.location.origin) return;
@@ -3015,6 +3024,7 @@ console.log('FLOWDECK v2.4.6 — IIFE done, _wsInitData keys:', Object.keys(wind
   <!-- Offline banner -->
   <div class="offline-banner" x-show="!online" x-transition>
     <span>{{ fd_icon('alert-triangle',14) }} You are offline. Changes will sync when connection is restored.</span>
+    <span class="offline-badge" x-show="pendingSyncCount > 0" x-text="pendingSyncCount + ' modification(s) en attente'"></span>
   </div>
 
   <!-- Move-to modal -->