Improve navigation between main app, conditions, and dashboard

- Main app: split tagline into attribution + Station/Dashboard nav pills (always visible, styled with border/hover)
- Conditions page: add Dashboard → link and ← App back-link in header
- Dashboard: add Conditions link, rename App → ← Weather in header nav

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

app/public/dashboard.html

@@ -214,7 +214,8 @@ canvas.sparkline { display: block; width: 100%; height: 22px; margin-top: 0.4rem
   </div>
   <div class="header-right">
     <span class="station-name" id="stationName"></span>
-    <a href="/" class="logout">App</a>
+    <a href="/conditions" class="logout">Conditions</a>
+    <a href="/" class="logout">← Weather</a>
     <a href="/dashboard/logout" class="logout">Sign out</a>
   </div>
 </div>