feat(database): inline embed + Open button + side peek + title placeholder

- Page title placeholder: new pages created with empty title, CSS :empty::before shows 'New page' in gray
- Database is now inline embed within page (not full-page replacement)
- Embed block 'collection' renders database table via FlowDeckDB.renderInto()
- Open button in column 1 of each row opens page in side peek panel
- Side peek: iframe loading /pages/{id}?embed=1, close/fullscreen/resize
- DB scripts refactored as reusable DBInstance + global FlowDeckDB API

app/templates/base.html

@@ -756,7 +756,7 @@
 
       // ── Workspace context → create workspace item ──
       if (ctx.wsId > 0) {
-        var body = { name: 'Untitled', type: 'page' };
+        var body = { name: '', type: 'page' };
         if (ctx.isGitea) body.workspace_id = ctx.wsId;
 
         fetch('/api/local-workspace/items', {