Update downmix logic and skip intro feature

[fed1337]

Description

• Downmix Improvements: Added stereo downmix algorithms, admin-configurable audio boosts, and user-selectable audio language preferences.

[codecov]

Codecov Report

❌ Patch coverage is 83.39223% with 47 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/httpapi/me_playback_handlers.go	75.60%	7 Missing and 3 partials ⚠️
internal/transcode/audio_select.go	71.87%	5 Missing and 4 partials ⚠️
internal/auth/postgres/store.go	79.31%	3 Missing and 3 partials ⚠️
internal/httpapi/play_handlers.go	81.81%	4 Missing ⚠️
internal/access/service.go	33.33%	2 Missing ⚠️
internal/auth/playback_prefs.go	92.59%	1 Missing and 1 partial ⚠️
internal/httpapi/admin_handlers.go	0.00%	2 Missing ⚠️
internal/transcode/downmix.go	90.90%	1 Missing and 1 partial ⚠️
internal/transcode/ffargs.go	71.42%	1 Missing and 1 partial ⚠️
internal/transcode/job.go	77.77%	2 Missing ⚠️
... and 4 more

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[github-actions]

Allure Report Summary

	Scope	Duration	Stats	New	Flaky	Retry
	All tests	44s	⁠ 720 ⁠ 1	14	0	0

Reports: Awesome, Dashboard

[github-actions]

New Tests in sudoStream Allure Awesome Report

Show 14 new tests

• passed rewrites DEFAULT= on TYPE=AUDIO lines for user track index (0s)
• passed empty list normalizes to empty slice (0s)
• passed PATCH rejects more than three languages and bad JSON (233ms)
• passed update fails when auth store is unset (0s)
• passed matches eng preference to eng track language code (0s)
• passed empty stream list returns -1 (0s)
• passed GET and PATCH /api/me/playback-preferences persist languages (262ms)
• passed playback prefs return 500 when auth service unset (0s)
• passed playback prefs return 401 without login (232ms)
• passed playback prefs round-trip via auth service (202ms)
• passed playback languages empty when store is unset (0s)
• passed GET returns 500 when playback prefs cannot be loaded (200ms)
• passed postgres store persists audio language prefs on user (365ms)
• passed parseDownmixBoost applies algorithm defaults and bounds (0s)

[github-actions]

New Tests in sudoStream Allure Dashboard Report

Show 14 new tests

• passed rewrites DEFAULT= on TYPE=AUDIO lines for user track index (0s)
• passed empty list normalizes to empty slice (0s)
• passed PATCH rejects more than three languages and bad JSON (233ms)
• passed update fails when auth store is unset (0s)
• passed matches eng preference to eng track language code (0s)
• passed empty stream list returns -1 (0s)
• passed GET and PATCH /api/me/playback-preferences persist languages (262ms)
• passed playback prefs return 500 when auth service unset (0s)
• passed playback prefs return 401 without login (232ms)
• passed playback prefs round-trip via auth service (202ms)
• passed playback languages empty when store is unset (0s)
• passed GET returns 500 when playback prefs cannot be loaded (200ms)
• passed postgres store persists audio language prefs on user (365ms)
• passed parseDownmixBoost applies algorithm defaults and bounds (0s)