fix(import): read the Stalker import expiry through parseStalkerDate

The validated-import snackbar multiplied the raw account_info.expire_date
by 1000. Portals encode an unlimited account as -1, "0" or a zero date,
which announced a 1969/1970 expiry, and a date-string expiry rendered as
"Invalid Date". Every other consumer already reads the value through
parseStalkerDate; the import now does too, so the guide's "no notice
without a fixed expiry" holds (Codex review on #1851).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.changes/import-stalker-unlimited-expiry.md

@@ -0,0 +1,6 @@
+---
+type: fix
+area: import
+---
+
+Adding a Stalker portal with an unlimited subscription no longer announces a bogus 1970 expiry date, and a portal that reports its expiry as a date shows that date instead of "Invalid Date".