epic: Nextcloud ecosystem integration

[rubenvdlinde]

Summary

Track every component that surfaces or manages other Nextcloud apps' data inside @conduction/nextcloud-vue. The pattern is the same in every case:

• The OpenRegister backend already integrates with the target app (a <App>Service exists).
• The library is missing the matching UI surface — typically a tab inside CnObjectSidebar that lists / creates / unlinks the related entity.
• Apps using OpenRegister get the integration for free as soon as the component lands.

This epic groups the open ones, lists the obvious candidates, and is the place to file new sub-tasks as more NC apps get OpenRegister-side integration.

In scope

A component qualifies for this epic when all of these are true:

1. It surfaces or manipulates data that lives in another Nextcloud app (not in OpenRegister itself).
2. The OpenRegister backend already exposes the integration via a service / controller.
3. It is mountable inside CnObjectSidebar (the canonical placement for object-related cross-app data) or, when the integration is admin-facing, surfaces in a settings / management panel.

OpenRegister-internal UI work (audit export, webhook manager, semantic search bar, text-extraction status, chat widget) does not belong here — those are OpenRegister UI completeness, not ecosystem integration.

Open sub-tasks

• feat: CnDeckCardTab — create/view Deck cards from object sidebar #62 — CnDeckCardTab — create/view Deck cards from object sidebar
• feat: CnCalendarEventTab — create/view calendar events from object sidebar #61 — CnCalendarEventTab — create/view calendar events from object sidebar
• feat: CnFileVersionsModal — show file version history with restore #58 — CnFileVersionsModal — show file version history with restore

Candidates worth filing as the OR backend lands them

• CnTalkRoomTab — link an OpenRegister object to a Nextcloud Talk conversation, list participants, deep-link to the room
• CnMailThreadTab — surface linked emails for an object (replaces the current ad-hoc mail/X-OPENREGISTER-* patterns)
• CnTaskListTab — Nextcloud Tasks (CalDAV) integration, parallel to CnDeckCardTab
• CnContactCardTab — Nextcloud Contacts: link / display / create
• CnBookmarkTab — Nextcloud Bookmarks
• CnNotesTab — Nextcloud Notes
• CnPhotosTab — Nextcloud Photos / Memories album linkage
• CnFilesUploadDropzone — drag-drop upload that goes through Nextcloud Files (versions + permissions)

The OR side of these typically lands first via the integration registry (ADR-019) — when a new integration ships there, the matching Cn*Tab becomes the natural follow-up here.

How to add a new sub-task

1. Confirm the OR-side integration exists (search OpenRegister for <App>Service or the integration-registry leaf).
2. Open a new feat: issue in this repo with the same shape: Description / Requirements / Backend API / Acceptance.
3. Add it to the checklist above with - [ ] #<number>.
4. The new issue should reference this epic with Tracked by #<this-issue> so the back-link shows up automatically.

Out of scope

These are listed elsewhere or have their own homes:

• OpenRegister-internal UI surface (not cross-app): feat: CnChatWidget — AI chat widget with RAG context #63 feat: CnTextExtractionStatus — show extraction progress for uploaded files #60 feat: CnWebhookManager — admin UI for webhook CRUD and monitoring #59 feat: CnAuditExportDialog — export audit trail data #57 feat: CnSemanticSearchBar — expose OpenRegister semantic search #56
• Manifest renderer / dynamic page system: feat: implement JSON manifest renderer #89, feat(manifest): auto-wire useListView / useDetailView for type:index/detail pages #90