Add block document reference support to schema form

[devin-ai-integration]

Implements block document reference support for schema form properties. When a schema property has a blockTypeSlug field, it now renders a block document selector with optional inline creation instead of throwing a "not implemented" error.

This adds three new components:

• BlockDocumentCombobox: A searchable combobox for selecting block documents filtered by block type slug, with an optional "Create new" button
• BlockDocumentCreateDialog: A dialog for inline block document creation using the existing schema form and block creation patterns
• SchemaFormInputBlockDocument: A wrapper that integrates the combobox and dialog, outputting values in { $ref: blockDocumentId } format

The integration in schema-form-input.tsx replaces the previous throw new Error("not implemented") with the new component.

Related to #15512

Updates since last revision

• Added reactQueryDecorator to properties.stories.tsx to fix Storybook error for blockTypeSlug stories (they require QueryClientProvider for TanStack Query)

Screenshots

Human Review Checklist

• Verify the { $ref: blockDocumentId } format is the correct structure for block document references in Prefect schemas
• The type assertion in schema-form-input.tsx (line 82) casts value as { $ref: string } | undefined - confirm this is safe
• The as unknown as PrefectSchemaObject cast in block-document-create-dialog.tsx for blockSchema.fields - confirm this is safe
• The combobox does both server-side filtering (like_ in API query) and client-side filtering (filteredData) - this may be redundant

Checklist

• This pull request references any related issue by including "closes <link to issue>"
  • If no issue exists and your change is not a small fix, please create an issue first.
• If this pull request adds new functionality, it includes unit tests that cover the changes
• If this pull request removes docs files, it includes redirect settings in mint.json.
• If this pull request adds functions or classes, it includes helpful docstrings.

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Link to Devin run: https://app.devin.ai/sessions/36e0160cacd7477db78917771f4b27f4
Requested by: @desertaxle

[devin-ai-integration]

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