Implement native song story card sharing with lyrics selection

[Copilot]

Adds Instagram/Spotify-style story card generation and sharing for songs, with optional lyrics selection (max 5 lines), dominant color extraction from cover art, and adaptive layouts.

Core Infrastructure

• ISongStoryService: Color extraction, contrast calculation, story data preparation
• SongStoryData: Model containing song metadata, selected lyrics, extracted colors
• SongStoryService: SkiaSharp-based dominant color extraction with darkslateblue (#483D8B) fallback

Android Implementation

• AndroidSongStoryCardRenderer: Generates 1080x1920 PNG cards with dynamic layout (800px cover without lyrics, 400px with lyrics)
• LyricsSelectionDialogFragment: Material Design 3 dialog with RecyclerView, enforces 5-line max, live counter
• AndroidSongStoryShareService: Intent.ACTION_SEND integration
• FileProvider: Secure file sharing via cache directory
• Integrated share button in NowPlayingFragment

Windows Implementation

• WindowsSongStoryShareService: SkiaSharp rendering with DataTransferManager integration
• LyricsSelectionDialog: WinUI 3 ContentDialog with ItemsRepeater, 5-line enforcement
• Platform-specific fonts (Segoe UI vs sans-serif)

Technical Details

Color Extraction Algorithm:

• Samples pixels from cover art (every nth for performance)
• Filters transparent, very dark/light pixels
• Quantizes and selects most common color
• WCAG-compliant contrast calculation for text

Card Generation:

var storyService = services.GetService<ISongStoryService>();
var shareService = services.GetService<ISongStoryShareService>();

var storyData = await storyService.PrepareSongStoryAsync(song, selectedLyrics);
var cardPath = await shareService.GenerateStoryCardAsync(storyData);
await shareService.ShareStoryAsync(cardPath, "Played on Dimmer");

Layout Logic:

• Without lyrics: Centered 800px cover + large title/artist
• With lyrics: 400px cover + up to 5 lyrics lines with italic serif font
• "Played on Dimmer" branding footer
• All text auto-wrapped with proper line breaks

Services registered in DI containers: ServiceRegistration.cs (core), Bootstrapper.cs (Android), MauiProgram.cs (Windows).

Original prompt

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This section details on the original issue you should resolve

<issue_title>Song story sharing/lyrics sharing </issue_title>
<issue_description>I'd like to let it so that users can share any song in a card like way akin to Spotify or Apple music.
The card can have the song's dominant color from the cover image & if none, use darkslateblue.

Likewise users should be able to select lyrics lines at most 5 lines (a variable number) so as to show them in the card .

So if the song shared has no lyrics, show a big card & big cover image. If lyrics are added, show smaller cover image but highlight lyrics.

"Played on Dimmer" will be the little tag 😄

It would be native implementation, no MAUI for this.

I only wonder how lyrics selection will be on droid.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Song story sharing/lyrics sharing  #300

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