Menu: rename 'avianvisitors' link to 'github' + add built-by attribution

avian/api/menu.php: 4th drawer link label is now 'github' (shorter,
matches what the link actually points to).

avian/frontend/index.html: 'built by teddy' attribution sits below
the menu items (sibling of #dd-items inside #menu-dd) so it shows in
both local and forwarded modes. Drops the redundant 'built with
AvianVisitors' line that lived inside the lock screen - the github
menu item covers source-of-truth attribution.

avian/frontend/index.html

@@ -27,9 +27,9 @@
       <button type="submit" aria-label="unlock">→</button>
     </form>
     <p class="lock-hint" id="lockHint">enter password to unlock tools.</p>
-    <p class="built-by">built with <a href="https://github.com/Twarner491/AvianVisitors" target="_blank" rel="noopener">AvianVisitors</a></p>
   </div>
   <nav class="menu-items" id="dd-items"></nav>
+  <p class="built-by">built by <a href="https://theodore.net" target="_blank" rel="noopener">teddy</a></p>
 </aside>
 
 <main class="stage">
@@ -176,8 +176,7 @@
     <h2 id="aboutTitle">The birds outside your window</h2>
     <p class="about-body">A tiny microphone identifies every passing bird with Cornell's <a href="https://birdnet.cornell.edu/" target="_blank" rel="noopener">BirdNET</a>. Each species shows up as an illustration in the collage, sized by how often it's been heard.</p>
     <button type="button" class="about-explore" data-close="1">explore the birds →</button>
-    <p class="built-by">built by <a href="https://theodore.net" target="_blank" rel="noopener">teddy</a></p>
-  </div>
+    </div>
 </div>
 
 <nav class="slider" id="slider" aria-label="View">