fix(lists): enforce collaborator permissions end-to-end

[DSanich]

fix(lists): enforce collaborator permissions end-to-end (UI + mutations)

src/hooks/useVideoLists.ts already parses collaborative and collaborator tags, but src/pages/ListDetailPage.tsx still uses canEdit = isOwner (with a TODO).
As a result, collaboration metadata exists in events, but editing behavior remains owner-only in practice.

This issue aims to align list permissions across rendering and mutations so collaborative lists behave consistently and safely.

Problem

• Collaboration is represented in list metadata (collaborative, collaborator), but not fully enforced in app behavior.
• UI-level checks and mutation-level checks are not consistently aligned.
• A user can encounter unclear failure states when they appear to have access but edits are blocked (or vice versa).

Scope

• Implement a shared permission resolver for list editing:
  • owner can edit,
  • listed collaborators can edit when the list is collaborative,
  • everyone else is read-only.
• Replace local ad-hoc permission logic in list detail views with the shared resolver.
• Enforce the same permission model in list mutations (add/remove/edit), not only in UI visibility.
• Return clear, user-facing error messages for denied edit attempts.
• Keep public list reading behavior unchanged.

Out of scope

• Private/encrypted list support.
• New collaboration roles beyond owner/collaborator.
• Relay/protocol changes to list event format.

Definition of done

• Allowed collaborators can edit collaborative lists end-to-end.
• Non-collaborators cannot edit even if they trigger actions manually.
• UI affordances (buttons/dialogs) match actual backend/mutation permissions.
• Permission logic is centralized and reused (no drift between page and hooks).
• Existing owner-only flows continue to work without regressions.

[DSanich]

@rabble @jalcine @NotThatKindOfDrLiz @mbradley

I analyzed the repository for various issues and, as a result, created this task. I think it's important, so I'm working on it.

[DSanich]

@jalcine @mbradley @NotThatKindOfDrLiz Created PR #352

Resolved the TODO for collaborator permissions on lists by centralizing permission logic and enforcing it in both UI and mutations.

Would appreciate a review.

cc @rabble