Initial haunt-fm implementation

Full music recommendation pipeline: listening history capture via webhook,
Last.fm candidate discovery, iTunes preview download, CLAP audio embeddings
(512-dim), pgvector cosine similarity recommendations, playlist generation
with known/new track interleaving, and Music Assistant playback via HA.

Includes: FastAPI app, SQLAlchemy models, Alembic migrations, Docker Compose
with pgvector/pg17, status dashboard, and all API endpoints.

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

.env.example

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+# PostgreSQL
+POSTGRES_DB=hauntfm
+POSTGRES_USER=hauntfm
+POSTGRES_PASSWORD=changeme
+
+# Database URL (constructed in docker-compose, override for local dev)
+DATABASE_URL=postgresql+asyncpg://hauntfm:changeme@localhost:5432/hauntfm
+
+# Last.fm API
+HAUNTFM_LASTFM_API_KEY=
+
+# Home Assistant
+HAUNTFM_HA_URL=http://192.168.86.51:8123
+HAUNTFM_HA_TOKEN=
+
+# CLAP model
+HAUNTFM_MODEL_CACHE_DIR=/app/model-cache
+HAUNTFM_AUDIO_CACHE_DIR=/app/audio-cache
+
+# Embedding worker
+HAUNTFM_EMBEDDING_WORKER_ENABLED=true
+HAUNTFM_EMBEDDING_BATCH_SIZE=10
+HAUNTFM_EMBEDDING_INTERVAL_SECONDS=30