fix: eliminate x-data quoting bug by moving page data to JSON script tag

Root cause: x-data HTML attribute with tojson creates quote conflicts
that survive even Cache-Control: no-store (likely nginx proxy cache).

Solution: page data is now in a <script type=application/json> tag,
completely decoupled from Alpine x-data HTML attribute. Zero quoting
issues regardless of page content.

- x-data="editorState()" + x-init="loadPage()" replaces editor(...)
- Server passes page_data dict, template renders as JSON script tag
- Same approach used for page_share_mode and page_published
- All 73 tests pass

app/routers/board.py

@@ -752,7 +752,8 @@ async def view_page(request: Request, page_id: int):
         ).fetchone()
     ctx = {**sidebar, "page": page, "page_favorited": fav is not None,
            "page_share_mode": page.get("share_mode", "private"),
-           "page_published": bool(page.get("published", 0))}
+           "page_published": bool(page.get("published", 0)),
+           "page_data": {"id": page_id, "title": page.get("title"), "content_format": page.get("content_format", "blocks"), "content": page.get("content", ""), "favorited": fav is not None, "share_mode": page.get("share_mode", "private"), "published": bool(page.get("published", 0))}}
     template = env.get_template("page_editor.html")
     response = template.render(**ctx)
     return HTMLResponse(content=response, headers={"Cache-Control": "no-store, max-age=0"})