Fix critical playback crashes, cache expiry bug, and improve lyrics caching

[nakchwalabhi]

🚀 Summary

This PR fixes multiple critical and medium-level issues affecting playback stability, caching, and performance in the app.

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🔴 Critical Fixes

1. Stream URL Cache Expiry Bug

• Fixed incorrect expiry logic for cached stream URLs
• Previously, expiry time was stored as a relative value instead of absolute timestamp
• This caused stale URLs to be reused, leading to playback failures (403 errors) after a few hours

✅ Fix:

• Store expiry as: currentTimeMillis + expiresInSeconds
• Validate using proper time comparison

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2. Double unbindService() Crash

• Fixed crash caused by calling unbindService() twice
• onStop() already unbinds the service, so calling it again in onDestroy() caused:
  IllegalArgumentException: Service not registered

✅ Fix:

• Removed duplicate unbind call in onDestroy()

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3. NullPointerException in Stream Handling

• Fixed unsafe force unwraps (!!) on nullable fields:
  • url
  • contentLength

✅ Fix:

• Added proper null checks
• Throw PlaybackException(ERROR_CODE_NO_STREAM) when URL is null
• Skip DB operations when contentLength is null

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🟡 Medium Fixes

4. Lyrics Not Cached

• Lyrics fetched from network were not being cached

✅ Fix:

• Added LRU cache storage after successful fetch

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5. Inconsistent Cache Key in LyricsHelper

• Different cache keys used in different methods (mediaId vs artist-title)
• Resulted in cache misses

✅ Fix:

• Standardized cache key to mediaId

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6. MIME Type Parsing Crash

• split("codecs=")[1] could throw IndexOutOfBoundsException

✅ Fix:

• Replaced with safe parsing using getOrNull(1)
• Added null checks before DB operations

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🎯 Impact

• 🚫 Eliminates playback crashes and service lifecycle crash
• 🎧 Fixes long-session playback failures (stale stream URLs)
• ⚡ Improves performance by enabling lyrics caching
• 🧠 Makes code safer by removing unsafe null handling
• 🛠 Improves overall stability and reliability

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🧪 Testing

• Verified playback works correctly after extended usage
• Confirmed no crashes on service lifecycle events
• Tested lyrics caching across multiple songs

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📌 Notes

• No breaking changes introduced
• Existing architecture and behavior preserved
• Changes are minimal and focused on stability and correctness