What does this PR do?

Removes the PrismaMock-based unit test for duplicateHandler and replaces it with an integration test that uses Prisma directly against a real database. This aligns with the codebase's migration away from PrismaMock and eliminates all as any casts (there were 10+ in the old test).

• Old: duplicate.handler.test.ts — mocked Prisma, mocked EventTypeRepository, 10+ as any / eslint-disable lines
• New: duplicate.handler.integration-test.ts — real DB records, real handler execution, zero as any

Follows the established integration test pattern from listWithTeam.handler.integration-test.ts and getEventTypesFromGroup.integration-test.ts.

Handler bug fix

The duplicateHandler catch block was swallowing intentional TRPCErrors (e.g. FORBIDDEN, NOT_FOUND) and re-throwing them as INTERNAL_SERVER_ERROR. Added an early instanceof TRPCError check to re-throw them as-is. This was discovered because the integration test for non-team-member access was receiving INTERNAL_SERVER_ERROR instead of the intended FORBIDDEN.

Test coverage (7 tests)

1. Duplicates an individual event type (title, slug, length)
2. Preserves schedulingType: MANAGED on duplication
3. Copies hosts but not children for managed event types
4. Sets parentId to null on duplicated managed event types
5. Allows team members to duplicate managed event types
6. Rejects non-team members with FORBIDDEN
7. Returns CONFLICT on duplicate slug (unique constraint violation)

How should this be tested?

TZ=UTC VITEST_MODE=integration yarn vitest run packages/trpc/server/routers/viewer/eventTypes/heavy/duplicate.handler.integration-test.ts

Requires a running Postgres database with migrations applied (yarn workspace @calcom/prisma db-migrate).

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. N/A
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

Human Review Checklist

• Handler catch block change (duplicate.handler.ts:228-230): Now re-throws TRPCError instances before the generic INTERNAL_SERVER_ERROR fallback. This is a production behavior change — previously FORBIDDEN and NOT_FOUND were incorrectly returned as INTERNAL_SERVER_ERROR to clients.
• createCtx helper (integration test line 12-21): Uses as NonNullable<TrpcSessionUser> with only id and profile.id populated. This follows the pattern in getEventTypesFromGroup.integration-test.ts, but verify the handler doesn't access other TrpcSessionUser fields in paths exercised by these tests.
• Slug conflict test (integration test line 250-280): Asserts only code: "CONFLICT" — the handler has a more specific "duplicate_event_slug_conflict" message branch for when meta.target includes "slug". The P2002 meta.target for the @@unique([userId, slug]) constraint may not match — worth verifying the slug-specific error path is reachable.
• Cleanup in afterAll: Deletes hosts, event types, memberships, teams, and users in order. Confirm cascade behavior is handled correctly if any beforeAll step partially fails.

Link to Devin run: https://app.devin.ai/sessions/d6a4ad26a26140a2b7d70a5519e2636e
Requested by: @alishaz-polymath