Sharing: invite people to a document by email

[Adron]

Same as the list invites, against /api/documents/{id}/invites (GET/POST) and DELETE /api/documents/{id}/invites/{token}.

Acceptance criteria

• Service methods on Services/InterlinedApiClient.Documents.cs.
• Pending invites listed with address, role and Revoke in the document's share UI.
• Subscriber-gated with the same locked-but-visible treatment.
• Shares one invite component with the list flow rather than duplicating it.

[Adron]

Implemented in #169 (stacked on #168) — work continues in the PR from here.

The document invite endpoints are live-verified and wired into the document Share card via a new Services/InterlinedApiClient.DocumentInvites.cs partial, leaving the contended .Documents.cs untouched. Per the acceptance criteria it shares the exact same Views/InvitePanel control as the list flow rather than duplicating it — the invite payloads turned out byte-identical, so this PR only adds a service partial, a target adapter, one factory line and one view line, and the panel leads the Share card the way the web does.

The one real difference from lists is the ownership envelope (document vs data), handled in the new partial. No invite was sent to a real address — probes used the reserved .invalid TLD on a throwaway document that has since been deleted.