fix(dashboard-mobile): clear Android status bar, footer-nav overlap, fetch toast spam

- Header.css: mobile padding-top is additive (var(--space-md) + env(safe-area-inset-top)) so the brand row keeps its 12px breathing room below the Android status bar instead of having it replaced by the inset.
- ExecutorStatusBar.css: bottom offset now uses max(env(safe-area-inset-bottom), 12px) to match the floor MobileNavBar already applies, so the footer lands flush on top of the nav instead of inside its padding band.
- useToast.ts: silently drop bare "Failed to fetch" error toasts (from fetch() aborts on tab background/resume); toasts with additional context still pass through.

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

packages/dashboard/app/components/ExecutorStatusBar.css

@@ -291,7 +291,11 @@
     font-size: 11px;
     height: calc(var(--space-lg) * 2 + var(--space-xs));
     overflow: hidden;
-    bottom: calc(var(--icb-bottom-offset, 0px) + var(--mobile-nav-height) + env(safe-area-inset-bottom, 0px) + var(--standalone-bottom-gap));
+    /* Must match the mobile nav bar's effective height. MobileNavBar floors
+       the bottom inset to 12px (Android Chrome under-reports the inset while
+       its address bar is collapsing), so we have to use the same floor here
+       or the footer ends up drawn inside the nav's padding area. */
+    bottom: calc(var(--icb-bottom-offset, 0px) + var(--mobile-nav-height) + max(env(safe-area-inset-bottom, 0px), 12px) + var(--standalone-bottom-gap));
   }
 
   .executor-status-bar__segment {