fix(editor): repair block identity for template pages (duplicate/reordered lines)

Template-created pages (weekly report, project doc, meeting notes, to-do
list, ...) were persisted without block ids. The editor assigned ids
client-side, but the realtime room loaded the raw id-less content and sent
it back on 'sync'; applySync then merged id-less server blocks with local
blocks, producing data-bid='undefined' collisions and duplicated/shuffled
lines as soon as the user edited. Editing an empty page was unaffected
because the server state was empty.

Fixes:
- board.use_page_template: materialize unique block ids (recursively) when
  instantiating built-in or user templates.
- realtime_server: unique block_id() (uuid) + ensure_block_ids() on room
  load and on insert ops.
- editor: recursive ensureBlockIds() in init; gtTok() now restores
  [[fddate:...]] tokens (date chips survived as labels before).
- realtime client: applySync() normalizes ids, no longer appends unknown
  local blocks (duplication), and keeps local content when server is empty.

Tests: pytest (templates + realtime) and Playwright e2e covering to-do
list, weekly report date chip, Enter ordering and legacy id-less repair.

app/templates/_page_editor_scripts.html

@@ -25,6 +25,11 @@ window.__fdEditorScriptsLoaded = true;
     {name:'ACTIONS',items:[{id:'duplicate',name:'Duplicate',icon:'▣'},{id:'turn_into',name:'Turn into…',icon:'↩'},{id:'copy_link',name:'Copy link to block',icon:'🔗'},{id:'delete',name:'Delete block',icon:'✕'}]}];
 
     let _bid=0;function genId(){return 'b'+(++_bid)+'_'+Date.now().toString(36);}
+    // v5.13.1: guarantee every block (and nested child) has a stable id.
+    // Template blocks may be persisted without ids; leaving them undefined
+    // makes `data-bid="undefined"` collide and corrupts editing.
+    function ensureBlockIds(list){if(!Array.isArray(list))return list;list.forEach(function(b){if(b&&typeof b==='object'){if(!b.id)b.id=genId();if(Array.isArray(b.children))ensureBlockIds(b.children);}});return list;}
+    window.ensureBlockIds=ensureBlockIds;
     function cp(e){const s=window.getSelection();if(!s.rangeCount)return 0;const r=s.getRangeAt(0).cloneRange();r.selectNodeContents(e);r.setEnd(s.getRangeAt(0).endContainer,s.getRangeAt(0).endOffset);return r.toString().length;}
     function gt(e){return (e&&e.innerText!==undefined)?e.innerText:(e?e.textContent:'');}
     // v5.11.0: read a contenteditable block back to plain text, converting
@@ -39,6 +44,7 @@ window.__fdEditorScriptsLoaded = true;
           if(n.nodeType===3){out+=n.nodeValue;continue;}
           if(n.nodeType===1){
             if(n.classList&&n.classList.contains('fd-wiki-chip')){out+=n.getAttribute('data-token')||'';continue;}
+            if(n.classList&&n.classList.contains('fd-wiki-date')){out+=n.getAttribute('data-token')||'';continue;}
             if(n.tagName==='BR'){out+='\n';continue;}
             walk(n);
           }
@@ -1049,7 +1055,7 @@ window.__fdEditorScriptsLoaded = true;
           const dataEl=document.getElementById('page-data');
           if(dataEl){try{const data=JSON.parse(dataEl.textContent);this.pid=data.id;this.pageTitle=data.title||'';this.favorited=data.favorited||false;const fmt=data.content_format||'blocks';this.contentFormat=fmt;const raw=data.content||'';
           if(fmt==='file'){this.fileData=data;this.fileUrl=data.file_url||'';this.loadFileContent(data);}
-          else if(fmt==='blocks'&&raw){try{this.blocks=JSON.parse(raw);this.blocks.forEach(b=>{if(!b.id)b.id=genId()});}catch(e){this.blocks=[];}}
+          else if(fmt==='blocks'&&raw){try{this.blocks=JSON.parse(raw);ensureBlockIds(this.blocks);}catch(e){this.blocks=[];}}
           else if(raw&&raw.trim())this.blocks=this.md2b(raw);
           // v5.12.0: page lock + layout options
           this.isLocked=!!data.is_locked;this.lockedBy=data.locked_by||null;