feat(0.6.2): current version badge on Settings page

Small grey pill follows the "Radio — Settings" H1 — v{RADIO_VERSION}.
Visible at a glance so you don't have to hover the plugin row in
Plugins → Installed or open About just to check what version you're on.
Dark-theme variant so it stays readable when theme=dark.

Files: radio.php (version), inc/settings.php (<span> inside H1),
assets/css/radio.css (.radio-version-badge + dark override),
inc/about.php (rotate v0.6.2 into latest expanded slot, v0.6.1 into
earlier-releases list), CHANGELOG.md.

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

assets/css/radio.css

@@ -297,6 +297,22 @@
     font-size: 13px;
 }
 
+/* Small grey pill that follows the Settings page H1 — at-a-glance
+   confirmation of the version you are running (v0.6.2). */
+.radio-version-badge {
+    display: inline-block;
+    margin-left: 8px;
+    padding: 2px 8px;
+    background: #e2e4e7;
+    color: #50575e;
+    border-radius: 10px;
+    font-size: 11px;
+    font-weight: 600;
+    vertical-align: middle;
+    letter-spacing: 0.02em;
+}
+.radio-theme-dark .radio-version-badge { background: #2c3338; color: #c3c4c7; }
+
 /* ──────────────────────────────────────────────────────────────────
  * Dashboard widget — no nested card; bare content inside .inside
  * (WP renders the widget as a postbox already; don't double up)