fix(clickhouse): renumber task_kind migration 029 → 031

Migration 030_create_sessions_v1.sql landed on main on 2026-04-28 (PR #3417)
and was applied to test/prod ClickHouse on subsequent deploys. Migration
029_add_task_kind_to_task_runs_v2.sql was authored later on 2026-05-10 as
part of the Sessions primitive PR, after 030 was already at version 30 in
the goose history.

The next deploy fails because goose strict-mode refuses to apply a missing
version 'before' current_version 30:

  goose run: error: found 1 missing migrations before current version 30:
    version 29: 029_add_task_kind_to_task_runs_v2.sql

Renumber to 031 so goose applies it as the next version after 030. SQL is
unchanged.

Author: ericallam