fix: preview affichait du JSON brut au lieu du texte des pages FlowDeck

Ajout de _extractPreview(): parse le JSON Notion blocks, extrait le
texte des champs .content ou .text de chaque block. Fallback sur le
raw content si le format n'est pas blocks/markdown.

Avant: {"blocks":[{"type":"text","content":"Hello"}]}
Après: Hello

app/templates/local_workspace.html

@@ -504,11 +504,32 @@ document.addEventListener('alpine:init', function() {
         fetch('/api/local-workspace/page-content/' + node.id)
           .then(function(r) { return r.json(); })
           .then(function(d) {
-            self.previewContent = (d.content || '').substring(0, 500);
+            self.previewContent = self._extractPreview(d.content || '', d.format);
           })
           .catch(function() { self.previewContent = '(preview not available)'; });
       }
     },
+    _extractPreview(content, format) {
+      if (!content) return '(empty)';
+      // Try to extract text from Notion block JSON
+      if (format === 'blocks' || format === 'markdown') {
+        try {
+          var blocks = typeof content === 'string' ? JSON.parse(content) : content;
+          if (blocks && blocks.blocks && Array.isArray(blocks.blocks)) {
+            var lines = [];
+            for (var i=0; i<blocks.blocks.length && lines.length<20; i++) {
+              var b = blocks.blocks[i];
+              if (b.content) lines.push(b.content);
+              else if (b.text) lines.push(b.text);
+              else if (typeof b === 'string') lines.push(b);
+            }
+            return lines.join('\n').substring(0, 500) || '(empty)';
+          }
+        } catch(e) {}
+      }
+      // Fallback: raw text
+      return String(content).substring(0, 500);
+    },
     hidePreview() {
       this.previewVisible = false;
     },