[web] Remove SubscriptionFormatters, format subscription dates in the frontend (#36409)

* [web] Remove SubscriptionFormatters, format subscription dates in the frontend

Replace the server-formatted nextPaymentDueAt/nextPaymentDueDate/
trialEndsAtFormatted fields with the raw periodEnd date and format in
the React dashboard (same strings as before, English + UTC). Also
consolidate hand-rolled trial checks onto isInFreeTrial /
SubscriptionHelper.isInTrial.

* [web] Remove the now-unused dateformat dependency

* [web] Address review: payment-dates unit test, UTC dates in acceptance test

Add a dedicated unit test asserting the exact formatted strings from
formatPaymentDate/formatPaymentDateTime, and use explicit UTC timestamps
in the SubscriptionDashboard acceptance fixtures instead of
local-timezone Date constructors.

GitOrigin-RevId: 16ac4f1098b14ef9f1478d22cf39c1357ead7dea

services/web/package.json

@@ -130,7 +130,6 @@
     "crc-32": "^1.2.2",
     "csurf": "patch:csurf@npm%3A1.11.0#~/.yarn/patches/csurf-npm-1.11.0-c1b9cbb35b.patch",
     "csv": "^6.2.5",
-    "dateformat": "1.0.4-1.2.3",
     "ejs": "^3.1.10",
     "email-addresses": "^5.0.0",
     "eventsource-parser": "^1.1.2",
@@ -264,7 +263,6 @@
     "@types/bootstrap": "^5.2.10",
     "@types/chai": "^4.3.0",
     "@types/chai-as-promised": "^8.0.2",
-    "@types/dateformat": "^5.0.3",
     "@types/diff": "^5.2.3",
     "@types/dom-speech-recognition": "^0.0.7",
     "@types/events": "^3.0.3",