feat: add indexer and torrent REST controllers with service layer

- Add config module for yaml config (database, indexers, torrent)
- Add indexer module with Torznab protocol support
- Add IndexerService and TorrentService for business logic
- Add REST controllers for indexer search and torrent management
- Add Docker Compose for PostgreSQL and Jackett
- Add ERD documentation for database schema

docs/research/lidarr/research_summary.md

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+# Lidarr Database Research Summary
+
+## Overview
+
+Lidarr is a music collection manager that uses a **Release-based** system. Key design principles:
+
+1. **Metadata Separation** - Artist metadata separated from configuration
+2. **Release-Centric** - Works with releases, not loose tracks
+3. **Monitoring Hierarchy** - Artist → Album → Release (only one release monitored per album)
+4. **Quality Profiles** - Separate profiles for quality and metadata preferences
+5. **Download Lifecycle** - Pending → Queue → Imported → History/Blocklist
+
+## Core Entity Hierarchy
+
+```
+ArtistMetadata (1) ←→ (1) Artist (1) ←→ (N) Albums
+                                              ↓
+                                        (N) AlbumReleases (only 1 monitored)
+                                              ↓
+                                        (N) Tracks (N) ←→ (1) TrackFile
+```
+
+## Key Entities
+
+### Music Entities
+- **Artists** - Configuration (path, monitoring, profiles)
+- **ArtistMetadata** - Metadata (name, images, genres, members)
+- **Albums** - Album info with monitoring and search tracking
+- **AlbumReleases** - Physical releases (CD, Vinyl, Digital) - only ONE monitored per album
+- **Tracks** - Individual tracks linked to releases
+- **TrackFiles** - Actual files on disk with quality info
+
+### Configuration
+- **QualityProfiles** - Acceptable formats and upgrade cutoff
+- **MetadataProfiles** - Which album types to include (Studio, EP, Live, etc.)
+- **RootFolders** - Storage locations with defaults
+
+### Download Tracking
+- **PendingReleases** - Delayed downloads (waiting for better quality)
+- **DownloadHistory** - Download lifecycle events
+- **Blocklist** - Failed/rejected releases (prevent re-download)
+- **History** - Complete audit trail of all events
+
+### System
+- **Indexers** - Search sources (Newznab/Torznab)
+- **DownloadClients** - Torrent/Usenet clients
+- **ImportLists** - Auto-import from Spotify, Last.fm, etc.
+- **Tags** - Categorization
+
+## Monitoring States
+
+### Artist Level
+- `monitored` - Is artist being tracked
+- `monitor_new_items` - Policy for new releases (All/Future/Missing/Existing/None)
+
+### Album Level
+- `monitored` - Should we look for this album
+- `any_release_ok` - Auto-switch releases during import
+
+### Release Level
+- `monitored` - Is this the release we want (exactly ONE per album)
+
+## Download States
+
+```
+TrackedDownloadState:
+  Downloading → ImportPending → Importing → Imported
+                                         → Ignored
+            → DownloadFailed → DownloadFailedPending
+```
+
+## History Event Types
+
+- Grabbed - Download started
+- TrackFileImported - File imported to library
+- DownloadFailed - Download failed
+- TrackFileDeleted - File removed
+- TrackFileRenamed - File renamed
+- TrackFileRetagged - Metadata updated
+- AlbumImportIncomplete - Partial import
+- DownloadIgnored - Download skipped
+
+## Sources
+
+- GitHub: Lidarr/Lidarr
+- Key files:
+  - `src/NzbDrone.Core/Music/Model/Artist.cs`
+  - `src/NzbDrone.Core/Music/Model/Album.cs`
+  - `src/NzbDrone.Core/Music/Model/Release.cs` (AlbumRelease)
+  - `src/NzbDrone.Core/Music/Model/Track.cs`
+  - `src/NzbDrone.Core/MediaFiles/TrackFile.cs`
+  - `src/NzbDrone.Core/Datastore/Migration/001_initial_setup.cs`
+  - `src/NzbDrone.Core/Datastore/Migration/023_add_release_groups_etc.cs`