Initial commit: ym-dl with yandex-music-api-go library migration

Migrate ym-dl from custom oapi-codegen Yandex Music API client to external
gitea.mrixs.me/Mrixs/yandex-music-api-go library with token-only authentication.

Key changes:
- Replace custom Yandex API client with yandexmusic library wrapper
- Token-based OAuth authentication only (no username/password fallback)
- SQLite storage index with JSON index migration path
- Extended ID3 tag support: genre, comment, lyrics, publisher, ISRC, copyright
- High-resolution album covers (1000x1000)
- Fixed album download check (requires all tracks, not just one)

CLAUDE.md

@@ -0,0 +1,91 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+**ym-dl** — A Go service for monitoring and downloading tracks/albums from Yandex Music for configured artists.
+
+- **Language**: Go (strict typing, idiomatic patterns)
+- **Runtime**: Docker / Docker Compose
+- **API**: Yandex Music (OpenAPI spec at `docs/yandex-music.yaml`)
+- **Config**: YAML file listing artist IDs to monitor
+
+## Architecture
+
+```
+ym-dl/
+├── cmd/ym-dl/           # Main entry point
+├── internal/
+│   ├── config/          # Configuration loading (artist IDs, API credentials)
+│   ├── yandex/          # Yandex Music API client (generated from OpenAPI)
+│   ├── storage/         # Local file storage for downloaded tracks/albums
+│   ├── monitor/         # Periodic check logic for new releases
+│   └── downloader/      # Download orchestration
+├── docker-compose.yml   # Service definition
+├── Dockerfile           # Multi-stage build
+└── config.yaml.example  # Sample configuration
+```
+
+## Development Commands
+
+```bash
+# Build
+go build -o bin/ym-dl ./cmd/ym-dl
+
+# Run locally
+go run ./cmd/ym-dl --config config.yaml
+
+# Run with Docker Compose
+docker compose up --build
+
+# Run tests
+go test ./...
+
+# Run single test
+go test -v -run TestName ./internal/...
+
+# Lint
+golangci-lint run
+
+# Generate API client from OpenAPI
+oapi-codegen -generate types,client -package yandex docs/yandex-music.yaml > internal/yandex/client.gen.go
+```
+
+## Configuration
+
+`config.yaml` structure:
+```yaml
+yandex:
+  token: "oauth_token"        # Or use username/password for token exchange
+  username: "login"
+  password: "password"
+
+artists:
+  - id: 12345                 # Artist ID from Yandex Music
+  - id: 67890
+
+storage:
+  path: "/data/music"         # Local path for downloads
+  organize: true              # Organize into Artist/Album/Track structure
+
+monitor:
+  interval: "24h"             # Check interval (duration string)
+```
+
+## Key Implementation Notes
+
+- **Authentication**: Support both OAuth token and username/password (token exchange via `/token` endpoint)
+- **Rate limiting**: Respect Yandex API limits; implement exponential backoff
+- **Idempotency**: Track downloaded files by Yandex track/album ID to avoid re-downloads
+- **Progress**: Structured logging (JSON) for Docker environments
+
+## Docker
+
+Multi-stage build: builder (Go 1.23+) → runtime (distroless or alpine). Mount config at `/config.yaml`, storage at `/data`.
+
+## Testing
+
+- Unit tests for config, storage, monitor logic
+- Integration tests against mocked Yandex API (use `net/http/httptest`)
+- No real API calls in CI