Update module documentation

lib/music_library.ex

@@ -1,10 +1,29 @@
 defmodule MusicLibrary do
   @moduledoc """
-  Important contexts:
+  Music Library is an Elixir/Phoenix application for managing a personal music collection.
 
-  - `MusicLibrary.Artists` contains functions to access artists
-  - `MusicLibrary.Records` contains functions to access and manipulate records _irrespectively_ of being in the collection or wishlist
-  - `MusicLibrary.Collection` contains functions to access and manipulate records in the collection
-  - `MusicLibrary.Wishlist` contains functions to access and manipulate records in the wishlist
+  It provides comprehensive functionality for tracking music records, integrating with external
+  services, and analyzing listening habits.
+
+  ## Core Contexts
+
+  ### Record and Collection Management
+  - `MusicLibrary.Records` - Functions to access and manipulate records irrespectively of collection status
+  - `MusicLibrary.Collection` - Functions to access and manipulate records in the collection (purchased records)
+  - `MusicLibrary.Wishlist` - Functions to access and manipulate records in the wishlist (unpurchased records)
+  - `MusicLibrary.Artists` - Functions to access and manage artist information
+
+  ### Search and Discovery
+  - `MusicLibrary.Search` - Universal search functionality across records and artists
+  - `MusicLibrary.BarcodeScan` - Barcode scanning for quick record identification and import
+
+  ### External Service Integration
+  - `MusicLibrary.ScrobbleActivity` - Last.fm integration for scrobble tracking and statistics
+  - `MusicLibrary.ScrobbleRules` - Rules system for normalizing scrobbled track metadata
+
+  ### Content and Metadata Management
+  - `MusicLibrary.Colors` - Color extraction from album artwork using fast or slow algorithms
+  - `MusicLibrary.OnlineStoreTemplates` - Configurable templates for generating online store URLs
+  - `MusicLibrary.Secrets` - Encrypted storage for API keys and sensitive configuration
   """
 end