chore(db): finish Prisma cutover to Drizzle Kit tooling

Move CMS SQL to drizzle/migrations, drop prisma packages/schema, wire drizzle-kit scripts, and regenerate schema names from src/db/schema.ts.

Co-authored-by: Cursor <[email protected]>

drizzle/drafts/README.md

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+Draft SQL from `pnpm db:generate` (drizzle-kit). Never apply these automatically — copy reviewed statements into drizzle/migrations/ as numbered CMS migrations, then `pnpm db:migrate`.