feat: initial implementation of metadata aggregator

- gRPC service with MusicBrainz provider
- PostgreSQL schema with migrations
- Service layer with database-first caching
- Repository pattern for data access
- YAML configuration support
- Research documentation for 17 music metadata projects

docs/research/meelo/README.md

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+# Meelo
+
+## Overview
+
+Self-hosted personal music server designed for collectors and music maniacs. Focuses on flexibility, browsing, and listening experience with rich metadata support.
+
+## Key Features
+
+- **Stars**: 1,095
+- **Metadata Sources**: MusicBrainz, Genius, Wikipedia
+- **Parsing**: Embedded metadata or file names (or both)
+- **Lyrics**: Synced lyrics from embedded metadata and `.lrc` files
+- **Scrobbling**: ListenBrainz and Last.fm
+- **License**: GPL-3.0
+
+## Source
+
+| Resource | URL |
+|----------|-----|
+| **Repository** | https://github.com/Arthi-chaud/Meelo |
+| **Wiki** | https://github.com/Arthi-chaud/Meelo/wiki |
+| **Releases** | https://github.com/Arthi-chaud/Meelo/releases |
+
+## Key Features
+
+- Flexible metadata parsing (embedded tags or file structure)
+- External metadata enrichment (genres, descriptions, ratings)
+- Album artwork from embedded or external sources
+- YouTube artwork search for missing covers
+- User management with analytics
+- Web UI for browsing
+
+## Tech Stack
+
+- **Language**: TypeScript (87%), Python, Go
+- **Database**: PostgreSQL
+- **Deployment**: Docker
+
+## Self-Hosting
+
+```bash
+git clone https://github.com/Arthi-chaud/Meelo.git
+cd Meelo
+docker-compose up
+```
+
+## Notes
+
+- Designed for music collectors with large libraries
+- Requires "clean" collection (embedded metadata or standard folder structure)
+- Works well with iTunes or Beets pre-processed libraries
+- Active development (40 releases, latest v3.10.1)