[WIP] Add weighted shuffle mode for music tracks

[Copilot]

Weighted Shuffle Implementation Plan

• Create ShuffleMode enum (Random, Weighted/Smart)
• Add ShuffleMode property to AppStateModel and settings service
• Create IWeightedShuffleService interface
• Implement WeightedShuffleService with weight calculation algorithm
  • Calculate weights based on Rating, IsFavorite, PlayCompletedCount, SkipCount, LastPlayed
  • Handle hidden songs (weight = 0)
  • Implement weighted random selection algorithm
• Update EnumerableExtensions with WeightedShuffleInPlace method
• Update QueueManager to support weighted shuffle
• Update BaseViewModel ToggleShuffle to use weighted shuffle when enabled
• Add UI toggle for shuffle mode (Random vs Smart)
• Add comprehensive unit tests for weighted shuffle logic
• Manual testing and verification
• Security and code review

Original prompt

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This section details on the original issue you should resolve

<issue_title>Weighted / Probability-Based Shuffle (per track, rating & behavior driven)</issue_title>
<issue_description>Context
I came across a Reddit discussion where a user was looking for a music player that allows setting a probability for each track when using shuffle. Historically, this existed in Windows Media Player via ratings → probability, but modern players no longer support it well.
This aligns strongly with how Dimmer already models song behavior and intent.

Problem
Current shuffle modes are purely random and ignore:
user ratings
favorites
skip behavior
listening history
This makes “random” feel repetitive or disconnected from user taste.
Proposed Solution
Introduce a Weighted Shuffle (Smart Shuffle) mode where each song has a calculated weight instead of equal probability.
Selection is still random, but biased by user behavior.
Weight inputs (already available in Dimmer):
Rating
ManualFavoriteCount / IsFavorite
PlayCompletedCount
SkipCount
LastPlayed (recency)
Hidden songs → weight 0

Example behavior
Favorite + highly rated songs appear more often
Frequently skipped songs fade out naturally
Songs not played in a long time slowly regain weight
Hidden songs are never picked

Algorithm (high-level)
Compute a weight per song (integer ≥ 0)
Sum all weights
Pick a random number in [0..totalWeight)
Return the song whose cumulative weight contains that number

• Optional Enhancements to add too!

Cooldown window to avoid repeats
Playlist-scoped weighting
Toggle between:
Pure Random
Smart (Weighted)
Debug view: “Why this song was picked”

• Why this matters
  Preserves randomness while respecting taste
  No micromanagement required
  Differentiates Dimmer from most players
  Cross-platform friendly, no platform APIs needed

</issue_description>

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

• Fixes Weighted / Probability-Based Shuffle (per track, rating & behavior driven) #344

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