fix: remove content crossfade animation that caused lag on heavy pages

Also configure PWA service worker to use network-first for JS chunks
to prevent ChunkLoadError after deploys.

app/sites/[id]/SiteLayoutShell.tsx

@@ -1,7 +1,5 @@
 'use client'
 
-import { usePathname } from 'next/navigation'
-import { AnimatePresence, motion } from 'framer-motion'
 import SiteNav from '@/components/dashboard/SiteNav'
 
 export default function SiteLayoutShell({
@@ -11,24 +9,12 @@ export default function SiteLayoutShell({
   siteId: string
   children: React.ReactNode
 }) {
-  const pathname = usePathname()
-
   return (
     <>
       <div className="w-full max-w-6xl mx-auto px-4 sm:px-6 pt-8">
         <SiteNav siteId={siteId} />
       </div>
-      <AnimatePresence mode="popLayout">
-        <motion.div
-          key={pathname}
-          initial={{ opacity: 0 }}
-          animate={{ opacity: 1 }}
-          exit={{ opacity: 0 }}
-          transition={{ duration: 0.2, ease: 'easeOut' }}
-        >
-          {children}
-        </motion.div>
-      </AnimatePresence>
+      {children}
     </>
   )
 }