Restart backend with modular v2 architecture

[jackshim415]

Summary

• restart the backend around a Hono modular-monolith skeleton
• port the complete Prisma data model to Drizzle, including relations, constraints, enums, and generated Zod/OpenAPI schemas
• add authenticated account and API-key vertical slices with verified-team authorization

Verification

• bun run typecheck
• bun run lint
• bun run format:check
• bun run test (16 passing)
• drizzle-kit export

Notes

• the existing migration predates this restart and is intentionally not regenerated in this PR
• the unrelated untracked src/handler/file/answer.ts file is excluded