Fix React SDK rich text styles

[robert-moore]

Summary

• Restore dashboard-authored bold, italic, list, link, and media styling inside the React SDK's scoped CSS reset.
• Match the flow builder's compact rich-text rhythm and add a dedicated playground fixture.
• Stage the fix for release as @churnkey/react@0.7.2.

Root cause

The universal .ck-cancel-flow * reset applies font: inherit and removes padding. That flattened semantic bold and italic styles and removed list indentation and markers from HTML produced by the dashboard editor.

Impact

Dashboard-configured offer and step copy now renders bold, italic, ordered and unordered lists, links, responsive images, and video consistently in the default React SDK components.

Validation

• Workspace pre-push typecheck
• Workspace pre-push tests (React: 224 passed, 8 skipped; MCP: 235 passed)
• React package and playground production builds
• Real-browser visual verification using a TipTap-shaped rich-text fixture
• npm pack --dry-run for @churnkey/react@0.7.2