What does this PR do?

Fixes a behavioral regression introduced in #27497 where the listWithTeam SQL query was changed to add AND "public"."EventType"."teamId" IS NULL to the first part of the UNION. This caused team event types with userId set (but no corresponding Membership row) to silently disappear from query results.

This PR:

1. Removes the teamId IS NULL filter from Part 1 of the UNION, restoring the original behavior where all event types with userId = currentUser are returned (including team events where the user is the owner).
2. Adds a LEFT JOIN users to Part 2 of the UNION so both parts produce identical username values for overlapping events, ensuring UNION deduplication works correctly.
3. Adds 9 comprehensive integration tests covering previously untested edge cases.

Key scenarios now tested

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 — no documentation changes required.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

1. Run the integration tests:

   TZ=UTC VITEST_MODE=integration yarn test listWithTeam.handler.integration-test.ts

2. Verify all 9 test cases pass, especially:
   • "should return team event types where userId is set but user has no membership" — this is the regression test
   • "should not duplicate events when user is both owner and team member" — validates UNION dedup

Human Review Checklist

• Verify UNION deduplication: both UNION parts now JOIN to users on EventType.userId, so overlapping rows produce identical username values and are correctly deduped
• Confirm that removing teamId IS NULL from Part 1 doesn't produce unexpected results for other consumers (useEventTypes hook in bookings, atoms API controller)
• Validate the test for "team event where userId is set but no membership" correctly reproduces the regression scenario

Link to Devin run: https://app.devin.ai/sessions/db3ea4a75b23410080df845007f47c56
Requested by: @Ryukemeister