fix: replace the six Italian user-facing strings with the English wording already used elsewhere

None of them was an isolated slip — each already had an English twin somewhere
else in the system, so this is alignment rather than translation.

The four in `ws.rs` are the slash-command replies (/sethome, /cost x2,
/compact), and the Telegram plugin — the same command set, reached through a
different surface — has said them in English all along. The two surfaces could
answer the same command in two languages. Adopted Telegram's wording verbatim,
and made the /compact "nothing to summarise" line match its twin's spelling
while there.

The two in `skald-relay-server` are the APNs alert body. That one is worth not
re-deriving: it is the *fallback* shown only when the notification service
extension cannot run, and the iOS app localises the same message under the
English key "Action required" (Localizable.xcstrings, en + it). English was
already the canonical form on the other side of the wire — the hardcoded Italian
only ever surfaced in the one case where no locale is negotiated with anyone.

crates/skald-relay-server/src/push.rs

@@ -78,7 +78,7 @@ impl PushItem {
         match self.kind() {
             PushKind::Content => json!({
                 "aps": {
-                    "alert": { "title": "Skald", "body": "Azione richiesta" },
+                    "alert": { "title": "Skald", "body": "Action required" },
                     "badge": 1,
                     "sound": "default",
                     "mutable-content": 1,
@@ -93,7 +93,7 @@ impl PushItem {
             }),
             PushKind::Wake => json!({
                 "aps": {
-                    "alert": { "title": "Skald", "body": "Azione richiesta" },
+                    "alert": { "title": "Skald", "body": "Action required" },
                     "badge": 1,
                     "sound": "default",
                     "content-available": 1