[BjoernSchotte]

Motivation

We use this server so that an assistant can plan events for a group: create a calendar, share it, put
(recurring) events in it with a video link, and open a Talk room that guests can join. Doing this for real people
showed some gaps: times without an offset were taken as UTC, a bad RRULE reached Nextcloud, there was no way to
give a Talk room a guest password or lobby, no join link was returned, and nothing kept the assistant from
changing events that other people own. This PR closes these gaps. It is independent of #87 (multi-user mode) and does not need it.

Changes

Talk

• create_conversation and get_conversation return url, the link to join (<base>/index.php/call/<token>;
  works without pretty URLs; the token is URL-encoded).
• New set_conversation_password (write): sets the password guests need for a public conversation. Removing the
  password needs destructive. The password is never echoed, also not in error messages.
• New set_conversation_lobby (write): turns the lobby on (optionally until a future time) or off.

Clearer error for apps that are not available (OCS 998)

Nextcloud answers OCS 998 ("Invalid query, please check the syntax") when no route matches. Under apps/<id>/
this means the app does not serve this account: not installed, disabled, or limited to groups the user is not in
(seen with Talk restricted to some groups). The error now says so. App-level 404s keep their own message.

Calendar events

• Time zones: NEXTCLOUD_MCP_TIMEZONE (IANA name, validated at start) and a timezone tool argument. Times
  without an offset are wall time in that zone; events get TZID and a VTIMEZONE, so a weekly event stays at
  19:00 across daylight saving changes. Without either setting, times stay UTC as before. get_events accepts
  offsets in the range. Moving only the start keeps the duration; an end before the start is refused.
• RRULE checks: only DAILY..YEARLY, known parts, COUNT/INTERVAL at most 1000, never COUNT and
  UNTIL together. UNTIL is converted to UTC (or a date for all-day events), as RFC 5545 requires.
• conference_url: stored as CONFERENCE (RFC 7986) and as LOCATION when that is empty (as Nextcloud
  Calendar does for Talk rooms), else as a Video call: <url> line in the description. Only http(s) URLs are
  accepted. update_event can replace or remove it.
• Safety for events of other people: create_event marks events with X-NC-MCP-CREATED-BY:<user id>.
  update_event refuses events without the caller's mark, or with attendees (Nextcloud would send them
  notifications), unless allow_foreign=true, so that a client can ask its user first. update_event and
  delete_event take an optional expected_summary and refuse to act if the title differs. Event output shows
  has_attendees and created_by_me, never attendee or organizer addresses.

Calendar administration (new tools)

create_calendar (unique URI from the name, also avoiding URIs of trashed calendars; optional group share in the
same call), share_calendar / unshare_calendar (users and groups, read or read-write), publish_calendar /
unpublish_calendar (public read-only link), delete_calendar (destructive, with an expected_name guard; for a
sharee it removes the calendar from their account only) and get_calendar_shares (owner only).
get_calendar_shares uses Depth 1 on the calendar home, because Nextcloud omits owner-principal with Depth 0.

search_files: refuse ..

The SEARCH scope is now built from the path's segments: empty and . segments are dropped, and .. is refused
with a clear error before a request is sent. Before, a/../.. went to Nextcloud and failed there with an unclear
error. The scope is deliberately not percent-encoded: SearchDAV's PathHelper takes a relative scope href as
a path without URL-decoding it; the existing integration test for a folder named search #1 %41 Ü depends on this.

Security considerations

• The conversation password is never returned, also not in error messages.
• Removing a conversation password and deleting a calendar need the destructive level; all other new tools are
  write, get_calendar_shares is read.
• conference_url accepts only http/https (no javascript: etc.).
• The creator mark and expected_summary/expected_name guards make it harder for an assistant to change or
  delete the wrong thing in shared calendars. They are guards, not access control: Nextcloud's own permissions
  still decide.
• .. in search_files paths is refused before a request is sent.

Tests

• Unit: tests/test_talk_admin.py (join link, password, lobby), tests/test_client_errors.py (OCS 998),
  tests/test_calendar_helpers.py (time zones, RRULE, conference URL, guards, slugs, principals),
  tests/test_files_helpers.py (_search_scope).
• Integration: tests/integration/test_calendar_guard.py (time zones across DST, bad RRULE creates nothing,
  video link, shared calendar <uri>_shared_by_<owner>: the read-write sharee writes, the owner needs
  allow_foreign, a read-only sharee cannot write) and tests/integration/test_calendar_admin.py (group share
  visible to the member, sharees see no shares and cannot share, publish/unpublish, delete guard), plus the ..
  case in tests/integration/test_files.py. These ran against Nextcloud 34 during development.
• Locally on Python 3.12: ruff check, ruff format --check, isort --check src/ and pyright are clean; 773
  unit tests pass.
• README and PROGRESS.md list the 9 new tools; scripts/sync_progress.py maps the new calendar test modules,
  and the counts were recomputed with it.

Backwards compatibility

• Without NEXTCLOUD_MCP_TIMEZONE and without the timezone argument, times without an offset are UTC, as before.
• New tool arguments are optional.
• Behaviour change: update_event now refuses events that this server did not create, or that have attendees,
  unless allow_foreign=true. Events created before this change carry no mark, so updating them needs
  allow_foreign=true once. If you prefer this guard to be opt-in, I am happy to change it.
• RRULE values that were accepted before but are invalid or unbounded (e.g. COUNT with UNTIL) are now refused.

AI disclosure: this change was written with Claude Code (Claude Opus 5.5); commits carry a Co-Authored-By trailer.

🤖 Generated with Claude Code

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