Add mobile bottom tab bar for small screen navigation

- New MobileTabBar component with Home, Search, and Account tabs
- Animated indicator follows active tab (spring layoutId transition)
- Shown only below sm breakpoint where desktop nav links are hidden
- Account tab provides quick sign-out access
- Safe area padding for devices with home indicators
- Added bottom padding to layout to prevent content overlap

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

app/(pages)/layout.tsx

@@ -3,6 +3,7 @@
 import { CommandPalette } from "@/components/command-palette";
 import { KeyboardHelpDialog } from "@/components/keyboard-help-dialog";
 import { KeyboardProvider } from "@/components/keyboard-provider";
+import { MobileTabBar } from "@/components/mobile-tab-bar";
 import { NavBar } from "@/components/nav-bar";
 import { Toaster } from "@/components/ui/sonner";
 
@@ -13,7 +14,7 @@ export default function PagesLayout({
 }) {
   return (
     <KeyboardProvider>
-      <div className="min-h-screen">
+      <div className="min-h-screen pb-14 sm:pb-0">
         <NavBar />
         {/* Ambient glow */}
         <div className="pointer-events-none fixed left-1/2 top-1/4 -translate-x-1/2 -translate-y-1/2 h-[600px] w-[800px] rounded-full bg-primary/3 blur-[200px]" />
@@ -21,6 +22,7 @@ export default function PagesLayout({
           {children}
         </main>
       </div>
+      <MobileTabBar />
       <CommandPalette />
       <KeyboardHelpDialog />
       <Toaster position="bottom-right" />