fix: lower sidebar breakpoint from md to sm so desktop sidebar renders

Responsive variants (md:flex, md:hidden) were silently missing from the
Tailwind CSS bundle due to stale build cache — sidebar was always hidden.
Changed breakpoint to sm (640px) and use rm -rf .next before builds.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CPf5Rc8QPx6V8KLEEgfKEQ

components/layout/sidebar.tsx

@@ -151,7 +151,7 @@ export function Sidebar({ role, userName, userEmail }: SidebarProps) {
   return (
     <>
       {/* Desktop sidebar */}
-      <aside className="hidden md:flex fixed left-0 top-0 h-full w-60 bg-white border-r border-gray-200 flex-col z-40">
+      <aside className="hidden sm:flex fixed left-0 top-0 h-full w-60 bg-white border-r border-gray-200 flex-col z-40">
         {/* Header */}
         <div className="flex items-center justify-between px-4 py-4 border-b border-gray-100">
           <span className="text-base font-bold text-gray-900 tracking-tight">IMS</span>
@@ -200,7 +200,7 @@ export function Sidebar({ role, userName, userEmail }: SidebarProps) {
       </aside>
 
       {/* Mobile bottom tab bar */}
-      <nav className="md:hidden fixed bottom-0 left-0 right-0 bg-white border-t border-gray-200 flex z-40 safe-area-pb">
+      <nav className="sm:hidden fixed bottom-0 left-0 right-0 bg-white border-t border-gray-200 flex z-40 safe-area-pb">
         {mobileItems.map(item => {
           const exactRoots = ['/reporter', '/supervisor', '/management', '/capa-owner', '/admin', '/report', '/account']
           const isActive = exactRoots.includes(item.href)