V74: Drop integer id/_id columns, promote uuid to PK on Category B tables.

V72 renamed id → uuid on 30 Category A tables. V73 fixed prerequisites (NOT NULL, unique indexes, dynamic PK code). V74 completes the migration by:

1. Drop all FK constraints referencing id on phoenix_kit_% tables
2. Drop integer FK columns across all tables (both Category A and B)
3. Drop bigint id + make uuid PK on Category B tables

After V74, every PhoenixKit table has uuid as its PK column. No integer id or _id columns remain.

All operations are idempotent (IF EXISTS / dynamic introspection guards).