fix: move speed controls to bottom of screen, use regularMaterial

Speed pill was floating mid-screen (padding.bottom 90). Moved to
bottom (padding.bottom 8) to sit just above the tab bar area.
Switched from ultraThinMaterial to regularMaterial for better
Liquid Glass look with more opacity and stronger blur.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ios/Platform/Platform/ContentView.swift

@@ -113,11 +113,11 @@ struct MainTabView: View {
                                 .frame(width: 32, height: 32)
                         }
                     }
-                    .padding(.horizontal, 14)
-                    .padding(.vertical, 8)
-                    .background(.ultraThinMaterial, in: Capsule())
-                    .shadow(color: .black.opacity(0.1), radius: 8, y: 2)
-                    .padding(.bottom, 90)
+                    .padding(.horizontal, 16)
+                    .padding(.vertical, 10)
+                    .background(.regularMaterial, in: Capsule())
+                    .shadow(color: .black.opacity(0.15), radius: 12, y: 4)
+                    .padding(.bottom, 8)
                     .transition(.move(edge: .bottom).combined(with: .opacity))
                 }
                 .animation(.spring(duration: 0.3), value: isAutoScrolling)