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>

docker-compose.yml

@@ -0,0 +1,121 @@
+version: "3.9"
+
+# ClickTrack — full self-hosted stack
+# Usage: docker compose up -d
+# First run: docker compose up -d --build
+
+services:
+
+  # ── Next.js application ──────────────────────────────────────────────────────
+  app:
+    build:
+      context: .
+      dockerfile: docker/Dockerfile
+    restart: unless-stopped
+    depends_on:
+      postgres:
+        condition: service_healthy
+      redis:
+        condition: service_healthy
+    environment:
+      DATABASE_URL: postgres://clicktrack:${POSTGRES_PASSWORD:-clicktrack}@postgres:5432/clicktrack
+      REDIS_URL: redis://redis:6379
+      REGISTRY_REPO: ${REGISTRY_REPO:-}
+      REGISTRY_BRANCH: ${REGISTRY_BRANCH:-main}
+      NEXT_PUBLIC_APP_NAME: ${NEXT_PUBLIC_APP_NAME:-ClickTrack}
+      MUSICBRAINZ_USER_AGENT: ${MUSICBRAINZ_USER_AGENT:-ClickTrack/0.1 (self-hosted)}
+      NODE_ENV: production
+    expose:
+      - "3000"
+    networks:
+      - internal
+
+  # ── PostgreSQL 16 ─────────────────────────────────────────────────────────────
+  postgres:
+    image: postgres:16-alpine
+    restart: unless-stopped
+    environment:
+      POSTGRES_DB: clicktrack
+      POSTGRES_USER: clicktrack
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-clicktrack}
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+      - ./docker/init.sql:/docker-entrypoint-initdb.d/01-init.sql:ro
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U clicktrack -d clicktrack"]
+      interval: 5s
+      timeout: 5s
+      retries: 10
+    networks:
+      - internal
+
+  # ── Redis 7 ───────────────────────────────────────────────────────────────────
+  redis:
+    image: redis:7-alpine
+    restart: unless-stopped
+    command: redis-server --save 60 1 --loglevel warning
+    volumes:
+      - redis_data:/data
+    healthcheck:
+      test: ["CMD", "redis-cli", "ping"]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+    networks:
+      - internal
+
+  # ── Nginx reverse proxy ───────────────────────────────────────────────────────
+  nginx:
+    image: nginx:1.27-alpine
+    restart: unless-stopped
+    depends_on:
+      - app
+    ports:
+      - "${HTTP_PORT:-80}:80"
+      - "${HTTPS_PORT:-443}:443"
+    volumes:
+      - ./docker/nginx.conf:/etc/nginx/conf.d/default.conf:ro
+      # Mount TLS certificates here for HTTPS (optional):
+      # - /etc/letsencrypt:/etc/letsencrypt:ro
+    networks:
+      - internal
+
+  # ── Registry sync (optional cron container) ───────────────────────────────────
+  registry-sync:
+    build:
+      context: .
+      dockerfile: docker/Dockerfile
+    restart: unless-stopped
+    depends_on:
+      postgres:
+        condition: service_healthy
+    environment:
+      DATABASE_URL: postgres://clicktrack:${POSTGRES_PASSWORD:-clicktrack}@postgres:5432/clicktrack
+      REDIS_URL: redis://redis:6379
+      REGISTRY_REPO: ${REGISTRY_REPO:-}
+      REGISTRY_BRANCH: ${REGISTRY_BRANCH:-main}
+      NODE_ENV: production
+    # Run the sync script on a cron schedule inside the container.
+    # Requires REGISTRY_REPO to be set; the container exits cleanly if not.
+    command: >
+      sh -c '
+        while true; do
+          node -e "
+            const { syncRegistry } = require(\"./lib/registry/sync\");
+            syncRegistry().then(r => console.log(\"Sync:\", JSON.stringify(r))).catch(console.error);
+          " || true;
+          sleep ${REGISTRY_SYNC_INTERVAL:-3600};
+        done
+      '
+    profiles:
+      - registry
+    networks:
+      - internal
+
+volumes:
+  postgres_data:
+  redis_data:
+
+networks:
+  internal:
+    driver: bridge