fix: app cache and other issues (#5460)

* fixes

* #[serde(untagged)] my BEHATED (still kinda broken)

* remove unused hasContent ref

* clean up code in fetch instance

* ping 3 times for average latency

* fix: pinging to be more accurate

TCP_NODELAY — Set on the TCP stream right after connect, preventing Nagle's algorithm from buffering the small ping packet (could save up to ~40ms)

Instant over Utc::now() — Switched to monotonic std::time::Instant for timing, which is more precise and designed for measuring elapsed time (still using chrono just for the ping magic value)

* delete useFetch util and just use native fetch

* rename worlds until functions for more clarity

* fix lint

* fix cache.rs logic

* make backend ping use both impls

* Add optional timeout to server ping

* fix gallery appearing in nav with no items

* remove EU countries and add EU option for server country

* add uk to europe

---------

Co-authored-by: aecsocket <aecsocket@tutanota.com>

apps/app-frontend/src/helpers/worlds.ts

@@ -231,6 +231,25 @@ export function isLinkedWorld(world: World): boolean {
 	return world.type === 'server' && !!world.linked_project_id
 }
 
+export async function getServerLatency(
+	address: string,
+	protocolVersion: ProtocolVersion | null = null,
+): Promise<number | undefined> {
+	const pings: number[] = []
+	for (let i = 0; i < 3; i++) {
+		try {
+			const status = await get_server_status(address, protocolVersion)
+			if (status.ping != null) {
+				pings.push(status.ping)
+			}
+		} catch {
+			// Ignore individual ping failures
+		}
+	}
+	if (pings.length === 0) return undefined
+	return Math.round(pings.reduce((sum, p) => sum + p, 0) / pings.length)
+}
+
 export async function refreshServerData(
 	serverData: ServerData,
 	protocolVersion: ProtocolVersion | null,