fix: bw/stats 404, gateway links, history crash

- swr.ts: remove useBandwidth(), drop bw from useDashboard()
- events/route.ts: skip bandwidth SSE (Kubo 0.28.0 unsupported)
- usage/page.tsx: remove getBWStats call + bw references
- helpers.ts: gatewayLink -> ipfs.maos.dedyn.io (subdomain only)
- upload/page.tsx: fix local gatewayLink (subdomain only)
- storage.ts: update default gatewayUrl, add defensive getHistory()

public/sw.js

@@ -69,6 +69,11 @@ self.addEventListener('fetch', (event) => {
   // Same-origin only
   if (url.origin !== self.location.origin) return;
 
+  // Only cache GET/HEAD — POST/PUT/DELETE/OPTIONS can't use Cache API
+  if (request.method !== 'GET' && request.method !== 'HEAD') {
+    return; // pass through, no caching
+  }
+
   // 1. Static assets → cache-first
   if (isStaticAsset(url)) {
     event.respondWith(cacheFirst(request, STATIC_CACHE));
@@ -98,7 +103,8 @@ async function cacheFirst(request, cacheName) {
   if (cached) return cached;
   try {
     const response = await fetch(request);
-    if (response.ok) {
+    // Cache API supports GET/HEAD only
+    if (response.ok && request.method === 'GET') {
       const cache = await caches.open(cacheName);
       cache.put(request, response.clone());
     }
@@ -111,7 +117,8 @@ async function cacheFirst(request, cacheName) {
 async function networkFirst(request, cacheName) {
   try {
     const response = await fetch(request);
-    if (response.ok) {
+    // Cache API supports GET/HEAD only — POST/PUT/DELETE must be skipped
+    if (response.ok && request.method === 'GET') {
       const cache = await caches.open(cacheName);
       cache.put(request, response.clone());
     }
@@ -129,7 +136,7 @@ async function staleWhileRevalidate(request, cacheName) {
 
   const fetchPromise = fetch(request)
     .then((response) => {
-      if (response.ok) cache.put(request, response.clone());
+      if (response.ok && request.method === 'GET') cache.put(request, response.clone());
       return response;
     })
     .catch(() => cached);