fix(0.6.1): About page restructure — balance the layout

By v0.6.0 the About page had eight version-history entries, each a
full paragraph, dwarfing the other cards and pushing Credits + thanks
off the visible area.

- Three short cards on top (What / Who / Credits) — equal-height,
  balanced row. Credits gets equal billing instead of being a fourth
  card buried under a wall of version notes.
- Version history is its own full-width card below. Only the latest
  release is shown in full; earlier releases collapse to one line
  each. The card now stays compact however many versions ship —
  adding a future release adds one line, not a paragraph.
- Full prose for older versions lives in CHANGELOG.md on Gitea via
  the existing "View the full CHANGELOG.md →" link. Single source of
  truth.

Files: radio.php (version), inc/about.php (3-card top + new
.radio-about-versions block with __latest / __earlier sub-elements;
9 versions in the earlier-releases list incl. v0.1.0),
assets/css/radio.css (drop dead .radio-about-card--versions rules;
add .radio-about-versions + __latest + __earlier; dark-theme overrides).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

radio.php

@@ -5,7 +5,7 @@
  * Plugin Name: Radio
  * Plugin URI:  https://icanhelp.ie/radio
  * Description: A small, focused, free radio player for your WordPress admin. 44 SomaFM stations grouped by 10 genres — ambient, electronic, lounge, rock, metal, jazz, world, reggae, holiday, specials. Plays via HTML5 audio; volume + station choice persist per-user.
- * Version:     0.6.0
+ * Version:     0.6.1
  * Requires at least: 5.0
  * Requires PHP: 7.4
  * Author:      David Keane
@@ -20,7 +20,7 @@
 if ( ! defined( 'ABSPATH' ) ) { exit; }
 
 // Plugin coordinates.
-if ( ! defined( 'RADIO_VERSION' ) )   { define( 'RADIO_VERSION',   '0.6.0' ); }
+if ( ! defined( 'RADIO_VERSION' ) )   { define( 'RADIO_VERSION',   '0.6.1' ); }
 if ( ! defined( 'RADIO_FILE' ) )      { define( 'RADIO_FILE',      __FILE__ ); }
 if ( ! defined( 'RADIO_PATH' ) )      { define( 'RADIO_PATH',      plugin_dir_path( __FILE__ ) ); }
 if ( ! defined( 'RADIO_URL' ) )       { define( 'RADIO_URL',       plugin_dir_url( __FILE__ ) ); }