fix(yt): ensure clean logout, purge WebView cookies/storage, and stop auto-reconnection

[ajisth69]

Overview

Resolves the issue where logging out / disconnecting from YouTube Music did not work, left lingering cookies in the WebView, or immediately re-connected the previous account.

Root Causes Identified

1. CookieManager.removeAllCookies was fire-and-forget: In YtMusicAuthManager.signOut(), removeAllCookies(null) was invoked asynchronously without awaiting completion or wiping HTML5 WebStorage, leaving residual session cookies and tokens in the WebView's cookie jar.
2. refreshCookiesFromCookieManager resurrected disconnected accounts: refreshCookiesFromCookieManager() lacked a guard on current.isConnected. Any background sync pass or API retry would re-read un-cleared cookies from CookieManager and auto-save the connection right back into preferences.
3. Premature cookie capture on Google login/account chooser: YouTubeLoginScreen's polling loop and webViewClient captured cookies on any URL as long as SAPISID was present, even while the user was on accounts.google.com trying to choose a different account.

Changes

• YtMusicAuthManager.kt:
  • Optimistically set _connection.value = YtConnection.DISCONNECTED immediately on signOut().
  • Run on Dispatchers.Main and suspend until CookieManager.getInstance().removeAllCookies completes, then flush() and deleteAllData() on WebStorage.
  • Guard refreshCookiesFromCookieManager() with if (!current.isConnected) return false so disconnected sessions are never revived.
• SettingsViewModel.kt:
  • Clear _ytChannels.value = emptyList() on disconnectYouTube().
  • Ensure confirmClearAllData() clears the YouTube session via ytAuthManager.signOut().
• YouTubeLoginScreen.kt:
  • Purge stale cookies and WebStorage upon entering the login screen.
  • Ensure session auto-capture only triggers when the redirect reaches music.youtube.com (or manually via 'I'm signed in').