Make createPage() and createFolder() context-aware

- createPage() now detects active workspace context (library, local-workspace page, sidebar)
- In a local/Gitea workspace: creates workspace item via /api/local-workspace/items with prompt
- No workspace: creates general Notion page via /board/api/pages (no prompt)
- Added hidden #fd-local-ws-id in local_workspace.html to expose workspace_id
- _confirmCreateFolder() passes workspace_id for Gitea workspaces
- Added _getContext() helper that checks multiple context sources in priority order
- Added _toast() helper for cross-component notifications

app/templates/local_workspace.html

@@ -10,6 +10,7 @@
 {% endblock %}
 
 {% block content %}
+<span id="fd-local-ws-id" hidden>{{ workspace_id }}</span>
 <div x-data="_wsInitData"
      @dragover.prevent="onDragOver($event)"
      @dragleave="onDragLeave($event)"