feat: initial scaffold for ClickTrack monorepo

Full self-hosted click track generator for cover bands.

Core technical pieces implemented:
- CTP (Click Track Protocol) TypeScript schema, Zod validator, and WAV
  renderer (44.1 kHz, 16-bit PCM, accented downbeats, ramp sections)
- MusicBrainz API client with 1 req/s rate limiting
- PostgreSQL schema (songs, tempo_maps, registry_sync_log) with triggers
- Git registry sync logic (clone/pull → validate CTP → upsert DB)
- Next.js 14 App Router: search page, track page, API routes
  (/api/songs, /api/tracks, /api/generate)
- UI components: SearchBar, SongResult, TempoMapEditor, ClickTrackPlayer
  (Web Audio API in-browser playback + WAV download)
- Docker Compose stack: app + postgres + redis + nginx + registry-sync
- Multi-stage Dockerfile with standalone Next.js output
- .env.example documenting all configuration variables
- README with setup instructions, CTP format spec, and API reference

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,35 @@
+# Dependencies
+node_modules/
+.pnp
+.pnp.js
+
+# Next.js
+.next/
+out/
+
+# Environment — NEVER commit .env
+.env
+.env.local
+.env.*.local
+
+# Build outputs
+dist/
+build/
+
+# Misc
+.DS_Store
+*.pem
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# TypeScript
+*.tsbuildinfo
+next-env.d.ts
+
+# Docker volumes (if mounted locally)
+postgres_data/
+redis_data/
+
+# Temporary registry clone
+/tmp/clicktrack-registry/