Let a hidden iCal calendar become visible again

An iCal subscription could be banished but never un-banished. The server has
always sent and accepted sidebar_hidden for subscriptions, but iOS left the
field off ICalSubscription entirely and omitted "ical" from
serverManagedSources, from setCalendarSidebarHidden and from both places that
reconcile the server's flag. So the key went into banishedCalendarKeys and
nothing ever took it out: refreshFromCache filters on that set as well as on
hiddenCalendarKeys, which is why showing the calendar again left its events
invisible and no amount of syncing helped. Closed on all four sides.

The account models are also no longer brittle about absent fields.
HomeAssistantAccount required auth_method, and CalDAVCalendar and
GoogleCalendar required sidebar_hidden, with no custom decoder — one missing
key threw, the `try?` at the call site turned that into an empty list, and the
reconciliation silently did not run, stranding calendars as banished in exactly
the same way. HACalendar already carried a lenient decoder for this reason; the
other three now do too.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ios/Calendarr iOS/Services/CalendarrAPI.swift

@@ -517,6 +517,7 @@ class CalendarrAPI {
         case "caldav":        path = "/api/caldav/calendars/\(calendarId)"
         case "google":        path = "/api/google/calendars/\(calendarId)"
         case "homeassistant": path = "/api/homeassistant/calendars/\(calendarId)"
+        case "ical":          path = "/api/ical/subscriptions/\(calendarId)"
         default:              return
         }
         _ = try await request(path, method: "PUT",