Stands up PageMoodboardHtml alongside PageMoodboard — renders the same
moodboard content (image/text/group nodes) entirely with absolutely-
positioned divs, CSS transforms, and pointer events. Shares the store
with PageMoodboard so switching tabs preserves the board.
- New page at app/src/pages/PageMoodboardHtml with HTML-only stage,
background grid, nodes, overlay transformer (8 resize handles + 1
rotate), marquee + lasso selection, viewport pan/zoom, paste and
gallery drop handlers, and a shortcut-aware text edit overlay.
- Reuses MoodboardStore, layout utilities, MoodboardToolbar,
TextEditOverlay, and the non-render interaction hooks from the
existing Konva moodboard unchanged.
- Experimental flag `moodboardHtmlPageEnabled` gates a new apps-menu
entry and a Settings → Experimental toggle.
- PageEditor: gallery drop targets the HTML stage element when the
MOODBOARD_HTML tab is active.