ux: replace generic cog admin-menu icon with closed-book (v3.3.5)

The WordPress admin sidebar showed "Logbook" with the generic
cog wheel icon (dashicons-admin-generic) — fine for a settings
page, off-brand for a plugin whose entire identity is "logbook".

Swapped to dashicons-book-alt (closed book) — the most literal
possible match in the Dashicons set, and visually reinforces the
brand at the first place users see the plugin every day.

Alternatives also viable (commented in the changelog for future
reference): dashicons-edit (pencil), dashicons-clipboard,
dashicons-welcome-write-blog, dashicons-format-aside.

VERSION
- wp-notes.php header 3.3.4 → 3.3.5
- WP_NOTES_VERSION constant 3.3.4 → 3.3.5
- About page version-history leads with v3.3.5; v3.3.4 demoted.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

inc/wp-notes-about.php

@@ -125,7 +125,11 @@ function wp_notes_about_page() {
                 <h2>Version history</h2>
                 <ul>
                     <li>
-                        <span class="ver">v3.3.4</span> &mdash; 25 May 2026 <span class="latest">latest</span><br>
+                        <span class="ver">v3.3.5</span> &mdash; 25 May 2026 <span class="latest">latest</span><br>
+                        New admin-menu icon: closed-book (<code>dashicons-book-alt</code>) replaces the generic cog wheel. Visually reinforces the &ldquo;Logbook&rdquo; identity in the WP sidebar.
+                    </li>
+                    <li>
+                        <span class="ver">v3.3.4</span> &mdash; 25 May 2026<br>
                         Repo renamed on Gitea: <code>a-wp-notes-v3</code> &rarr; <code>a-logbook</code>. The plugin&rsquo;s update checker and the &ldquo;View on Gitea&rdquo; / &ldquo;View all releases&rdquo; / &ldquo;View full CHANGELOG&rdquo; links now point at the new path. Local folder also renamed to <code>a-logbook</code>. The plugin&rsquo;s internal storage and slugs are unchanged &mdash; no data migration.
                     </li>
                     <li>