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/pages_test.go

@@ -63,7 +63,7 @@ func TestOverviewHeadFollowsTheCards(t *testing.T) {
 		`<h1 class="title is-3">Running, with warnings.</h1>`,
 		`class="sp-postmark sp-warn"`, `<b>WARN</b>`, `1 OF 6 CHECKS`,
 		`Needs attention: <a href="/server/health">TLS certificate</a> (Expires in 12 days).`,
-		`Updated 14:02:31 UTC`, `<p class="sp-kicker">mail.example.org</p>`,
+		`Updated 14:02:31`, `<p class="sp-kicker">mail.example.org</p>`,
 		`class="sp-warn"`, // the certificate card
 		`href="/server/health"`, `>All details</a>`,
 	)
@@ -154,7 +154,7 @@ func TestHealthShowsEveryCheckAndBothActions(t *testing.T) {
 		`<progress class="progress is-small is-success mb-1" value="12" max="100">`, `value="41"`,
 		`↓ 18.0 KiB/s`, `eth0: 2.1 GiB in, 6.4 GiB out`,
 		`pid 41, uptime 18 days`, `<span class="tag is-success is-light">running</span>`,
-		`2026-10-21 09:14 UTC`, `class="mt-4 has-text-danger"`, `Check that renewal on the host still works.`,
+		`2026-10-21 09:14`, `class="mt-4 has-text-danger"`, `Check that renewal on the host still works.`,
 		`dkim-signer <span class="sp-muted">· notifications</span>`, `unix:/run/selfpost/sign-local.sock`, `→ 203.0.113.25<br>← mail.example.org`,
 		`hx-get="/server/health/fragment"`,
 	)
@@ -346,6 +346,42 @@ func TestSettingsIsOneFormWithOneSaveButton(t *testing.T) {
 	pageHas(t, "Settings", out, `Save settings`, `<h1 class="title is-3">Settings</h1>`, `href="/account"`)
 }
 
+// The time zone is shown, not set: its name and offset, and a TZ the image
+// does not know is said to give UTC rather than named as the zone in use.
+func TestSettingsShowsTheTimeZone(t *testing.T) {
+	pageHas(t, "Settings", renderSignedIn(t, "settings", settingsFixture()),
+		`<h2>Time zone</h2>`, `<dd class="sp-mono">Europe/Moscow</dd>`, `UTC&#43;03:00. Set in <code>.env</code> (<code>TZ</code>); restart to change.`,
+		`and so are the stamps of <code>mail.log</code>.`)
+	now := time.Date(2026, 10, 17, 12, 0, 0, 0, time.UTC)
+	pageHas(t, "Settings without TZ", renderSignedIn(t, "settings", NewSettings(admin(), "30", "600 / h").WithTimeZone("", time.UTC, now)),
+		`<dd class="sp-mono">UTC</dd>`, `UTC&#43;00:00. Set in`)
+	pageHas(t, "Settings with a wrong TZ", renderSignedIn(t, "settings", NewSettings(admin(), "30", "600 / h").WithTimeZone("Mars/Olympus", time.UTC, now)),
+		`<dd class="sp-mono">Mars/Olympus</dd>`, `Not a zone this image knows, so the times are UTC.`)
+	ny, err := time.LoadLocation("America/New_York")
+	if err != nil {
+		t.Skipf("no zone America/New_York here: %v", err)
+	}
+	pageHas(t, "Settings in New York", renderSignedIn(t, "settings", NewSettings(admin(), "30", "600 / h").WithTimeZone("America/New_York", ny, now)),
+		`UTC-04:00. Set in`)
+}
+
+// The panel shows times in the container's zone, with no zone written
+// beside them (local-time): the row of a log, a message's page, the head
+// of Overview.
+func TestTimesAreTheContainersZone(t *testing.T) {
+	inZone(t, "Europe/Moscow")
+	at := time.Date(2026, 9, 21, 22, 30, 5, 0, time.UTC)
+	if got := FormatLogTime(at); got != "09-22 01:30:05" {
+		t.Errorf("FormatLogTime = %q, want the 22nd at 01:30:05 in Moscow", got)
+	}
+	if got := formatStamp(at); got != "2026-09-22 01:30:05" {
+		t.Errorf("formatStamp = %q", got)
+	}
+	if got := FormatReceived(at); got != "09-22 01:30" {
+		t.Errorf("FormatReceived = %q", got)
+	}
+}
+
 // Notifications are one switch for the instance, saved with the rest of the
 // page, and the records of the server's own name are drawn like a domain's.
 func TestSettingsNotificationsSwitchAndRecords(t *testing.T) {
@@ -477,7 +513,7 @@ func TestOverviewPageHasThePollAttributesAndNoOOBMark(t *testing.T) {
 func TestOverviewFragmentIsTheBoxAndTheHeadOutOfBand(t *testing.T) {
 	frag := renderFragment(t, "overview_poll", overviewFixture())
 	pageHas(t, "fragment", frag,
-		`<div class="sp-head" id="overview-head" hx-swap-oob="true">`, `class="sp-postmark sp-warn"`, `Updated 14:02:31 UTC`,
+		`<div class="sp-head" id="overview-head" hx-swap-oob="true">`, `class="sp-postmark sp-warn"`, `Updated 14:02:31`,
 		`<div class="box" id="health" data-poll aria-live="polite" hx-get="/overview/fragment" hx-trigger="load" hx-swap="outerHTML">`,
 		`Expires in 12 days`)
 	pageLacks(t, "fragment", frag, `<html`, `<body`, `navbar`, `<table`, `Outbound domains`)