refactor: make BeatDesign fully local-first

[erickkkyt]

Summary

• use local SQLite as BeatDesign's only workspace database and move migrations from drizzle/d1 to drizzle/sqlite
• default confirmed generation uploads to BeatAPI Files while retaining optional encrypted public R2/S3-compatible storage
• remove Wrangler, D1, Vercel, environment-loader, and obsolete SaaS-era repository artifacts
• synchronize the app, MCP server, and Codex plugin at v0.2.1

Verification

• pnpm install --frozen-lockfile
• pnpm build
• pnpm typecheck
• pnpm test — 328 passed, 0 failed, including real MCP stdio handshake
• pnpm i18n:check — 681/681
• pnpm audit --prod --audit-level high
• deterministic worktree and staged security scans
• pre-landing review and diff check