fix(0.7.1): Plugin Check follow-up — tested-up-to bump + .DS_Store re-cleanup

Re-ran PCP after v0.7.0 — issue count 169 → 4. Closes the only real
one of the four:

- Tested up to: 6.7 → 7.0 in readme.txt (PCP outdated_tested_upto_header).
  WordPress 7.0 is current.
- Stable Tag bumped to 0.7.1 in readme.txt.

Removed (again)
- .DS_Store files (root + assets/). macOS Finder regenerated them
  between PCP runs; they will not be present in the submission zip.

Known PCP residue (not addressable in source)
- .gitignore triggers a hidden_files WARNING on PCP. Keeping it is
  needed for git; will be excluded from the submission zip per WP.org
  packaging conventions.

Files: radio.php (version), readme.txt (Tested-up-to + Stable Tag +
new 0.7.1 changelog + upgrade notice), CHANGELOG.md,
inc/about.php (rotate v0.7.1 → latest, v0.7.0 → earlier list),
.DS_Store files deleted.

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

radio.php

@@ -5,7 +5,7 @@
  * Plugin Name: RangerHQ Radio
  * Plugin URI:  https://icanhelp.ie/radio
  * Description: A small, focused internet radio player for your WordPress admin. 44 hand-curated stations from SomaFM across 10 genres — ambient, electronic, lounge, rock, metal, jazz, world, reggae, holiday, specials. Plays via HTML5 audio; per-user station + volume + history + favourites; pop-out window for continuous background play.
- * Version:     0.7.0
+ * Version:     0.7.1
  * Requires at least: 5.3
  * Requires PHP: 7.4
  * Author:      David Keane
@@ -20,7 +20,7 @@
 if ( ! defined( 'ABSPATH' ) ) { exit; }
 
 // Plugin coordinates.
-if ( ! defined( 'RADIO_VERSION' ) )     { define( 'RADIO_VERSION',     '0.7.0' ); }
+if ( ! defined( 'RADIO_VERSION' ) )     { define( 'RADIO_VERSION',     '0.7.1' ); }
 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__ ) ); }