fix(v1.7.3): clean wordmark PNG + descender headroom

Regenerate assets/beep-wordmark.png (and -blue) as a clean transparent
render of the 3D logo, replacing the corrupted files — fixes the feed
header image. Bump the inline-SVG viewBox so the "p" descender never clips.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

beep.php

@@ -2,7 +2,7 @@
 /**
  * Plugin Name:       Beep
  * Description:       A Twitter-style microblog for WordPress, with likes, replies, and Gravatars. Use the [beep_feed] shortcode on any page.
- * Version:           1.7.2
+ * Version:           1.7.3
  * Requires at least: 6.0
  * Requires PHP:      7.4
  * Author:            Sami Ahmed
@@ -14,7 +14,7 @@ if (!defined('ABSPATH')) {
     exit;
 }
 
-define('BEEP_VERSION',     '1.7.2');
+define('BEEP_VERSION',     '1.7.3');
 define('BEEP_FILE',        __FILE__);
 define('BEEP_DIR',         plugin_dir_path(__FILE__));
 define('BEEP_URL',         plugin_dir_url(__FILE__));