proxy hosts get HTTP/2

Created with `http2_support: false`, so the live site runs HTTP/1.1 — six connections and everything
else queued behind them. Lighthouse costs it 900 ms, most of it the gallery images waiting on each
other.

Set in the defaults and again in `attach`, because HTTP/2 only means anything once there is a
certificate. A host created before this — both of them here — is secured but still on 1.1, and the
attach path is the one that can fix it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/ProxiesBlock.tsx

@@ -59,7 +59,15 @@ const NEW_HOST = {
   access_list_id: 0,
   certificate_id: 0,
   ssl_forced: false,
-  http2_support: false,
+  /*
+    HTTP/2. Only takes effect once a certificate is attached, which is why it is set here AND in
+    `attach` — a host created before it was secured would otherwise keep HTTP/1.1 forever, and
+    nothing in the panel would say so.
+
+    On HTTP/1.1 a browser opens six connections and queues everything else behind them, which on this
+    site meant the gallery images waited on each other. Lighthouse put it at 900 ms.
+  */
+  http2_support: true,
   hsts_enabled: false,
   hsts_subdomains: false,
   advanced_config: '',
@@ -177,6 +185,9 @@ export const ProxiesBlock = ({ servers }: { servers: Server[] }) => {
     await clientRef.current.put(`/proxy-manager/npm/nginx/proxy-hosts/${host.id}`, {
       certificate_id: certificateId,
       ssl_forced: true,
+      // The moment HTTP/2 becomes possible at all, so this is where it is turned on for a host that
+      // predates the default above.
+      http2_support: true,
     });
   };