* Scaffold Next.js + TypeScript + Tailwind project and core domain types

Adds project config (Next 14, TS, Tailwind dark studio theme), gitignore
updates, and the core type system (lib/types.ts) for the MPC + Elektron
hip-hop production copilot.

https://claude.ai/code/session_01JbAYny4cRVLnxpbGmvbwB9

* Implement Beatsmith: MPC + Elektron hip-hop production copilot MVP

Adds a local-first Next.js app that guides users through a 15-stage hip-hop
production workflow built around the MPC Live III (master clock + arranger),
Analog Rytm MKII (drums), and Analog Four MKII (bass/melody).

Features:
- 15-stage guided workflow with per-device guidance, creative option cards,
  context-aware idea generator, checklists, notes, and mark-complete controls
- 11 hip-hop substyles with BPM/groove/drum/bass/harmony/effects/arrangement
  characteristics and device-specific suggestions
- 166 seeded creative options (15+ per category) across drums, bass, chords,
  melody, samples, textures, effects, transitions, arrangement, automation, mix
- Rule-based idea generator scored by substyle, stage, BPM, mood, devices
- Arrangement builder with energy-coded timeline and per-section editors
- Editable hardware/MIDI/clock routing planner (defaults, not asserted specs)
- Song completion checklist, local persistence, JSON backup export/import
- Dark-mode studio UI; strong TypeScript types throughout

Builds clean, lint passes, all routes return 200.

https://claude.ai/code/session_01JbAYny4cRVLnxpbGmvbwB9

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Co-authored-by: Claude <noreply@anthropic.com>