Add prosemirror package for JSON parsing and HTML rendering

[codenem]

Summary

• Adds pkg/prosemirror with Go structs to unmarshal ProseMirror/Tiptap JSON documents (Node, Mark, and type-specific attribute structs using json.RawMessage for strict typing)
• Implements RenderHTML(node Node) (string, error) to convert parsed document trees to HTML, supporting all standard node types (headings, paragraphs, lists, tables, code blocks, images, blockquotes) and mark types (bold/strong, italic/em, underline, strike, code, link)
• Includes comprehensive test suite with a golden test against a full document fixture

Test plan

• make test MODULE=./pkg/prosemirror — all tests pass
• make lint — clean

🤖 Generated with Claude Code

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Summary by cubic

Adds pkg/prosemirror to parse ProseMirror/Tiptap JSON and render HTML, and introduces GraphQL dataloaders for faster, batched by-ID lookups in resolvers.

• New Features

  • pkg/prosemirror: Go structs for Node/Mark with strict attributes and RenderHTML(Node) supporting standard nodes/marks; golden tests included.
  • GraphQL dataloaders via github.com/vikstrous/dataloadgen; adds LoadByIDs (e.g., controls) and switches resolvers to batched fetches.

• Bug Fixes

  • Trust Center references: remove unused rank from item fragment and pass rank to the edit dialog.
  • DocumentList: add documentTypeFilter to refetch deps and wrap refetch in startTransition to avoid stale data.
  • Signature dialog copy: “Request signatures” and “requests created.”

^{Written for commit ebc71b7. Summary will update on new commits.}