Expand admin UI with full config editing and sp_dc cookie age tracking

- Fix auth status detection to use token validity instead of /me endpoint
- Add SessionCookieSetDate to SpotifyApiSettings for tracking cookie age
- Auto-set cookie date when updating sp_dc via admin UI
- Add edit buttons for all config settings (Spotify, Deezer, Qobuz, SquidWTF, Jellyfin)
- Show cookie age with color-coded expiration warnings (green/yellow/red)
- Display cookie age on both Dashboard and Config tabs
- Add generic edit setting modal supporting text/password/number/toggle/select inputs
- Remove SquidWTF base URL (not configurable)
- Add restart container button with manual restart instructions

allstarr/Models/Settings/SpotifyApiSettings.cs

@@ -63,4 +63,10 @@ public class SpotifyApiSettings
     /// Default: true
     /// </summary>
     public bool PreferIsrcMatching { get; set; } = true;
+    
+    /// <summary>
+    /// ISO date string of when the session cookie was last set/updated.
+    /// Used to track cookie age and warn when it's approaching expiration (~1 year).
+    /// </summary>
+    public string? SessionCookieSetDate { get; set; }
 }