feat: PWA offline capture — IndexedDB queue, service worker cache, auto-sync on reconnect

public/sw.js

@@ -0,0 +1,60 @@
+const CACHE_NAME = 'ims-v1'
+
+self.addEventListener('install', () => {
+  self.skipWaiting()
+})
+
+self.addEventListener('activate', event => {
+  event.waitUntil(
+    caches.keys().then(keys =>
+      Promise.all(keys.filter(k => k !== CACHE_NAME).map(k => caches.delete(k)))
+    )
+  )
+  self.clients.claim()
+})
+
+self.addEventListener('fetch', event => {
+  const url = new URL(event.request.url)
+
+  // Only handle same-origin GET requests under /ims/
+  if (
+    event.request.method !== 'GET' ||
+    url.origin !== self.location.origin ||
+    !url.pathname.startsWith('/ims/')
+  ) {
+    return
+  }
+
+  // Skip API routes — always go to network
+  if (url.pathname.startsWith('/ims/api/')) return
+
+  // Cache-first for immutable Next.js static assets
+  if (url.pathname.startsWith('/ims/_next/static/')) {
+    event.respondWith(
+      caches.match(event.request).then(cached => {
+        if (cached) return cached
+        return fetch(event.request).then(res => {
+          if (res.ok) {
+            const clone = res.clone()
+            caches.open(CACHE_NAME).then(c => c.put(event.request, clone))
+          }
+          return res
+        })
+      })
+    )
+    return
+  }
+
+  // Network-first for pages — fall back to cache when offline
+  event.respondWith(
+    fetch(event.request)
+      .then(res => {
+        if (res.ok) {
+          const clone = res.clone()
+          caches.open(CACHE_NAME).then(c => c.put(event.request, clone))
+        }
+        return res
+      })
+      .catch(() => caches.match(event.request))
+  )
+})