local-time: the panel in the container's zone, named on Settings

Agreed by the owner on 2026-10-13 (the local day, no "UTC" beside a
time); the zone is the container's TZ in .env and Settings only shows it,
his "Да" of 2026-10-17. Mockups c205106.

Every time the panel shows is formatted in time.Local and says no zone:
the logs' Time and the DMARC Received columns, a message's timeline,
Overview's "Updated", Health's certificate and renewal, the filter lists,
DMARC reports and windows, the auto limit's last recalculation. Stored
instants stay UTC. The days counted are the zone's: delivery_log_days and
sender_check_days key their rows by the local date, the sender check cuts
downtime at local midnights (byDay), the log filters' days run from local
midnight to local midnight. Notification mail and the test message write
the zone's abbreviation after a time - they are read away from the panel.
DMARC's one-day window label stays the reporter's (UTC) day.

Settings box 05, Time zone, read-only: the name (UTC without TZ), its
offset, and a TZ the image cannot load said to leave the times in UTC
(time/zoneinfo_unix.go, initLocal) rather than named. TZ is passed by the
compose file ("${TZ:-}"), in .env.example and the guide's table; tzdata is
named in the image (supervisor's python3.13 brings it today). Postfix
takes TZ through import_environment, so mail.log's stamps are the same
zone, which closes the trap the roadmap wrote down: the tailer has always
read them in time.Local.

Tests: a TestMain runs view, handlers, store and cmd/panel in UTC whatever
the machine's zone (as logtail's); TestSettingsShowsTheTimeZone,
TestTimesAreTheContainersZone, TestByDayInTheContainersZone, a Moscow day
in TestQueryInboundSpamFilters; envdoc's pattern takes two-letter names.
e2e time_zone_is_the_containers recreates the stand with
TZ=Europe/Moscow: date says MSK, Settings names the zone and UTC+03:00, a
test message's page gives its time and its mail.log lines in Moscow's.
go vet + go test (26 packages) and make e2e on the test server for this
tree.

Docs: guide (§ Settings, the TZ row, the days of Health and the logs),
architecture, schema-migrations, help (word for word with the mockup),
CHANGELOG [Unreleased] § Added, roadmap row done with the decision.

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

internal/web/view/help.go

@@ -263,7 +263,9 @@ var serverTopics = []HelpTopic{
 			" on either list. The only global user cannot be demoted or deleted, and you cannot delete the account you are signed in with. A new password set here signs that user out of their other sessions."),
 	}},
 	{ID: HelpSettings, Title: "Settings", Body: []Text{
-		Rich("Settings holds what is true of the whole instance. Log retention is how many days the Outbound log keeps its rows, from 7 to 365 and 90 by default; a sweep every six hours deletes older ones, and it is the main driver of how fast ",
+		Rich("Settings holds what is true of the whole instance. The time zone is the container's, ", Code("TZ"), " in ", Code(".env"),
+			" (UTC when it is not set): every time the panel shows and every day it counts is that zone's, as are the stamps Postfix writes in ", Code("mail.log"),
+			", so the two always agree; changing it is a restart of the container. Log retention is how many days the Outbound log keeps its rows, from 7 to 365 and 90 by default; a sweep every six hours deletes older ones, and it is the main driver of how fast ",
 			Code("/data"), " grows. With the inbound relay on there is a second number, for the Inbound log, with the same range. It does not change the rotation of ", Code("mail.log"),
 			", which is daily with about two weeks kept. The sending rate limit shown under it is level 1, the per-client-IP ceiling set in ",
 			Code(".env"), ": changing it needs a restart, and no level-2 limit can exceed it. Notifications are turned on or off here for everyone."),