refactor(web): mover Cambiar contraseña de sidebar a menu perfil [UDT-008]

La seccion Mi cuenta en el sidebar quedaba desprolija con un unico item.
Se movio Cambiar contraseña al dropdown del avatar en AppHeader donde
pertenece semanticamente.

src/web/src/components/layout/AppHeader.tsx

@@ -1,4 +1,4 @@
-import { Menu, LogOut, User } from 'lucide-react'
+import { Menu, LogOut, User, Lock } from 'lucide-react'
 import { useNavigate } from 'react-router-dom'
 import {
   Sheet,
@@ -85,6 +85,10 @@ export function AppHeader() {
             <User className="mr-2 h-4 w-4" />
             Mi perfil
           </DropdownMenuItem>
+          <DropdownMenuItem onClick={() => void navigate('/perfil/contrasena')}>
+            <Lock className="mr-2 h-4 w-4" />
+            Cambiar contraseña
+          </DropdownMenuItem>
           <DropdownMenuSeparator />
           <DropdownMenuItem onClick={handleLogout}>
             <LogOut className="mr-2 h-4 w-4" />

src/web/src/components/layout/AppSidebar.tsx

@@ -9,7 +9,6 @@ import {
   Users,
   ShieldCheck,
   KeyRound,
-  Lock,
 } from 'lucide-react'
 import { cn } from '@/lib/utils'
 import { Badge } from '@/components/ui/badge'
@@ -88,25 +87,6 @@ export function SidebarNav() {
           )
         })}
 
-        {/* Profile / account section — visible for all authenticated users */}
-        <div className="pt-2 pb-1 px-3">
-          <span className="text-xs font-semibold uppercase tracking-wider text-muted-foreground/60">
-            Mi cuenta
-          </span>
-        </div>
-        <Link
-          to="/perfil/contrasena"
-          className={cn(
-            'flex items-center gap-3 rounded-md px-3 py-2 text-sm transition-colors hover:bg-accent hover:text-accent-foreground',
-            pathname === '/perfil/contrasena'
-              ? 'bg-accent text-accent-foreground font-medium'
-              : 'text-muted-foreground',
-          )}
-        >
-          <Lock className="h-4 w-4 shrink-0" />
-          <span>Cambiar contraseña</span>
-        </Link>
-
         {/* Admin-only section */}
         {isAdmin && (
           <>