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/_page_editor_scripts.html

@@ -2350,12 +2350,21 @@ applyAIBlocks(text){
           if(this.saving){ if(cb) cb(); return; }
           this.sync();
           this.saving=true;
+          const blocksArr=this.blocks.map(b=>{const c={id:b.id,type:b.type,content:b.content};['checked','expanded','language','icon','src','embed_src','embed_provider','alt','style','embed_type','collection_id','dbs','file_name','file_size','file_mime','children','rows','align','has_header','first_col_header','colsW','meeting','automation_id','automation_name'].forEach(k=>{if(b[k]!=null)c[k]=b[k];});return c;});
+          // v6.0.0 PWA: hors ligne (ou échec réseau) → file IndexedDB rejouée au retour du réseau
+          const queueOffline=()=>{
+            if(!window.FlowOffline){this.saving=false;return;}
+            window.FlowOffline.savePageOffline({id:this.pid,title:this.pageTitle,content:JSON.stringify(blocksArr),content_format:'blocks'})
+              .then(()=>{this.saving=false;this.dirty=false;this.lastSaved='offline';if(cb)cb();})
+              .catch(()=>{this.saving=false;});
+          };
+          if(!navigator.onLine){queueOffline();return;}
           const csrf=document.cookie.match(/csrf_token=([^;]+)/);
-          fetch(`/board/api/pages/${this.pid}/blocks`,{method:'POST',headers:{'Content-Type':'application/json','X-CSRF-Token':csrf?csrf[1]:''},body:JSON.stringify({title:this.pageTitle,blocks:this.blocks.map(b=>{const c={id:b.id,type:b.type,content:b.content};['checked','expanded','language','icon','src','embed_src','embed_provider','alt','style','embed_type','collection_id','dbs','file_name','file_size','file_mime','children','rows','align','has_header','first_col_header','colsW','meeting','automation_id','automation_name'].forEach(k=>{if(b[k]!=null)c[k]=b[k];});return c;})})})
+          fetch(`/board/api/pages/${this.pid}/blocks`,{method:'POST',headers:{'Content-Type':'application/json','X-CSRF-Token':csrf?csrf[1]:''},body:JSON.stringify({title:this.pageTitle,blocks:blocksArr})})
           .then(r=>r.json()).then(()=>{this.saving=false;this.dirty=false;this.lastSaved=new Date().toLocaleTimeString();
             this._syncTitleUI();
             if(cb)cb();
-          }).catch(()=>{this.saving=false;});
+          }).catch(()=>{this.saving=false;queueOffline();});
         },
         runAutomationButton(bid){
           const idx=this.getIdx(bid);if(idx<0)return;