fix(database): save embed block properties (embed_type, collection_id, dbs, file_*)

The save() function's blocks.map() only copied 7 properties, missing:
embed_type, collection_id, dbs, file_name, file_size, file_mime.
Embed blocks lost their collection reference on save → page reload
showed empty page instead of database table.

app/templates/_page_editor_scripts.html

@@ -453,7 +453,7 @@
           const t=document.getElementById('_titleEl');if(t)this.pageTitle=t.textContent?.trim()||'New page';
           this.saving=true;
           const csrf=document.cookie.match(/csrf_token=([^;]+)/);
-          fetch(`/board/api/pages/${this.pid}/blocks`,{method:'POST',headers:{'Content-Type':'application/json','X-CSRF-Token':csrf?csrf[1]:''},body:JSON.stringify({title:this.pageTitle,blocks:this.blocks.map(b=>{const c={id:b.id,type:b.type,content:b.content};['checked','expanded','language','icon','src','alt','style'].forEach(k=>{if(b[k]!=null)c[k]=b[k];});return c;})})})
+          fetch(`/board/api/pages/${this.pid}/blocks`,{method:'POST',headers:{'Content-Type':'application/json','X-CSRF-Token':csrf?csrf[1]:''},body:JSON.stringify({title:this.pageTitle,blocks:this.blocks.map(b=>{const c={id:b.id,type:b.type,content:b.content};['checked','expanded','language','icon','src','alt','style','embed_type','collection_id','dbs','file_name','file_size','file_mime'].forEach(k=>{if(b[k]!=null)c[k]=b[k];});return c;})})})
           .then(r=>r.json()).then(()=>{this.saving=false;this.dirty=false;this.lastSaved=new Date().toLocaleTimeString();
             document.querySelectorAll(`.sidebar-item[data-page-id="page/${this.pid}"]`).forEach(item=>{const n=item.querySelector('.page-name');if(n)n.textContent=this.pageTitle||'New page';});
           }).catch(()=>{this.saving=false;});