Lists: extend ListSummary to the full live wire type #61

Gap

Models/ListSummary.cs models 6 of the 14 fields the API returns, dropping every field that drives hierarchy, folders, GitHub backing and provenance.

Live payload (GET /api/users/adron/lists, 2026-09-15)

{ "id":"...", "userId":"...", "messageId":null, "parentId":null, "folderId":null,
  "title":"dashingarrivals", "description":null, "isPublic":true, "metadata":null,
  "source":"github", "githubRepo":"Adron/dashingarrivals", "githubRepoPrivate":false,
  "createdAt":"...", "updatedAt":"..." }

What each unmodelled field unlocks

• parentId → parent/child list hierarchy + breadcrumbs
• folderId → list folders (/api/folders)
• source / githubRepo / githubRepoPrivate → GitHub-backed lists
• messageId → the list was created from a message ("Create from…")
• userId → ownership checks for owner-only affordances
• metadata → opaque; keep as raw JSON

Acceptance criteria

• All fields added; metadata kept as raw JSON so it round-trips.
• Owner-only affordances key off userId rather than inference.
• Existing Views/ListsView.xaml bindings keep working.