Duplicate an event type, with every child dataset

[distronode-com]

Fixes #17

Adds POST /v1/event-types/{slug}/duplicate and a Duplicate action on each row of the
event-types list.

What it copies

One transaction covers the event-type row plus every child dataset:

data	table	notes
intake questions	event_type_questions	label, type, options JSON, required, position
host assignments	event_type_hosts	user, role, priority
availability rules	availability_rules	event-type-specific rows only (see below)
reminder schedule	event_type_reminders	every hours_before
email subjects and notes	event_types.msg_* / subj_*	columns, so the row copy carries them

Bookings are not copied. A copied booking would be a meeting nobody agreed to, carrying a
live manage link, and it would distort both the per-invitee max_active_bookings cap and
the double-booking guard.

What is deliberately not inherited

• is_active is forced to 0. A copy exists to be edited; publishing one the moment it
  is created is the accident this endpoint has to avoid.
• archived_at is cleared. Archiving describes the original's lifecycle, and an
  archived copy would be invisible in the default list. The copy is inactive anyway, so
  nothing becomes bookable by clearing it.
• slug is regenerated as intro-call-copy, then intro-call-copy-2,
  intro-call-copy-3, … because event_types.slug is UNIQUE.

Everything else is copied verbatim, price_cents and currency included. Zeroing a
copied price is the more dangerous default: the operator sees a familiar event type,
publishes it, and starts taking free bookings for a paid meeting.

The name is copied verbatim too. Unlike the slug it is not required to be unique, and
it is booker-facing (it appears on the booking page, in confirmation emails and in the
calendar invite), so appending "(copy)" would risk leaking an internal artefact into
customer-facing copy. In the list the copy is distinguishable by its slug and by being
inactive. Happy to switch to Name (copy) if you would rather have it.

Implementation notes

• The row copy is one INSERT … SELECT. Every inherited column is named once and its
  value never passes through the Go process, so it cannot be zeroed or truncated in
  transit; the only literals in the statement are the four overridden fields.
• A drift gate keeps that column list honest. SQLite has no "copy every column" form,
  so the list is explicit — which means a future migration could silently leave a new
  column out of every copy, with no failing test anywhere near it.
  TestDuplicateEventType_handlesEveryEventTypeColumn reads
  pragma_table_info('event_types') and fails unless each column appears either in the
  copy or in a documented not-inherited list, and it also fails when a listed column
  disappears.
• Single-connection rule (ARCHITECTURE §4). Every child row is read into a slice, with
  each cursor closed, before anything is written — a write issued while a cursor is open
  would wait on the connection that cursor holds and deadlock as context deadline exceeded. Same shape as loadHostSchedule and the calendar reconciler.
• Global availability rules are not copied. A rule with event_type_id IS NULL is the
  host's global default and already applies to the copy. Copying it would promote a global
  rule into an event-specific one, after which the original's later edits would stop
  reaching the copy.
• Owner-scoped, like PATCH and DELETE. An assigned host sees an event type read-only,
  so handing them a copy they could not then edit would be worse than a 404.
• The slug is chosen inside the transaction, so the uniqueness check and the INSERT
  that consumes its answer are atomic. The check is deliberately not owner-scoped, because
  the constraint is not: a slug taken by another user's event type is still taken. After
  50 attempts it gives up with a 409 rather than looping.
• Response is 201 with the copy in the same shape as CreateEventType, so the admin UI
  can send the operator straight into the new event type's editor if you ever want that.

UI

A ghost icon button plus Tooltip in the row action group, between Settings and Archive,
shown only for event types the viewer owns — the same pattern the archive and delete
actions already use. On success it toasts the generated slug and notes that the copy is
inactive, then reloads the list. The button is disabled while its own request is in
flight, so a double click cannot produce two copies.

Testing

go test ./... green; gofmt -l . empty; go vet ./... clean. Frontend
pnpm test:visual passes (5 tests), as does pnpm check (941 files, 0 errors).

New tests in internal/handler/event_type_duplicate_test.go:

• copiesTheRowAndEveryChildDataset — seeds a non-default value in every copied column
  and one row in each child table, then asserts each dataset arrived, that child rows got
  fresh ids rather than being shared, that the global availability rule was left alone,
  and that no booking followed.
• slugIsUniqueAcrossTheInstance — -copy already owned by another user, so the first
  copy lands on -copy-2 and the second on -copy-3.
• archivedSourceProducesALiveDraft — archived source, un-archived and inactive copy.
• onlyTheOwnerMayDuplicate — an assigned host gets 404 and no copy is created.
• unknownSlugIs404.
• rollsBackWhenAChildCopyFails — a trigger forces the question insert to fail; asserts
  500 and that no event type, host, rule or reminder row survives. A partial copy would be
  worse than no copy: it looks like a real event type and is missing exactly the parts
  nobody thinks to check.
• handlesEveryEventTypeColumn — the drift gate described above.

[distronode-com]

I have read the CLA Document and I hereby sign the CLA

[github-actions]

All contributors have signed the CLA. ✅
_{Posted by the CLA Assistant Lite bot.}

[pullfrog]

✅ No new issues found.

Reviewed changes Initial review of duplicate event type (API + list UI + tests).

• Transactional duplicate endpoint — POST /v1/event-types/{slug}/duplicate copies the row via INSERT … SELECT and every child dataset (questions, hosts, event-scoped availability, reminders) in one tx; bookings and global availability rules stay out.
• Safe defaults — copy is inactive, un-archived, under a generated -copy/-copy-N slug; price and email template columns are preserved; owner-only like PATCH/DELETE.
• Admin list action — ghost icon + Tooltip Duplicate control on owned rows, with in-flight disable and a toast that names the new inactive slug.
• Test coverage — child fidelity, cross-user slug uniqueness, authz, rollback, event_types column drift gate, and explicit price/inactive + all nine email template columns.

  ^{｜ View workflow run ｜ Using Grok ｜ 𝕏}