feat(i18n): the interface speaks both languages

The account has had a `locale` since the beginning and it only chose which grammar
quick add read a line with — so picking English changed nothing anybody could see,
and the field said so honestly: "Sprog i hurtig tilføjelse". It says "Sprog" now,
because it means it.

Every component goes through `t()`. Danish is the source: a key missing from
English falls through to Danish rather than to the key, because a Danish sentence
in an English screen can be read and `settings.notifications.title` cannot.

`tag()` is the single place `Intl` is asked. Before, `'da-DK'` was written into a
dozen components, and that is the half of a translation that gets left behind — an
English interface still saying "24. aug." is exactly the shape of a job half done.
There is a smoke test that switches to English and refuses to see a Danish month
name in the calendar's heading.

Colour and theme names are keys now. `colors.js` keeps its ids untouched — they
are what the database stores, and `internal/store` reads them out of that file —
but `name` is `'color.tomato'`, resolved where it is drawn.

The Inbox keeps its name. It is a project row the server creates at signup, not a
string in the interface, and it can be renamed like any other project.

Four copies of "3 hours ago" became one, in `web/src/lib/when.js`. They had
already drifted: one said "aldrig logget ind", another "aldrig", and two stopped
at days where the others carried on to a date.

Routes stay Danish. `/indstillinger`, `/projekt`, `/uddelegeret` are bookmarks and
they are in every smoke test; translating them buys nothing and costs both.

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

web/src/lib/when.js

@@ -0,0 +1,51 @@
+/**
+ * How long ago something was, in the account's language.
+ *
+ * Four pages had a copy of this — the user list, the error log, the history page
+ * and the backup panel — and they had already drifted: one said "aldrig logget
+ * ind", another "aldrig", and two of them stopped at days while the others carried
+ * on to a date. Four copies is three chances for the fifth one to be different
+ * again.
+ *
+ * Written by hand rather than with `Intl.RelativeTimeFormat`, which would say
+ * "3 hours ago" and "for 3 timer siden" correctly and cannot say "lige nu" — and
+ * "just now" is the answer for most of what these lists show.
+ */
+import { t, tag } from './i18n.svelte.js';
+
+export function ago(iso, { never = 'when.never' } = {}) {
+	if (!iso) return t(never);
+
+	const then = new Date(iso);
+	const seconds = Math.round((Date.now() - then) / 1000);
+
+	if (seconds < 60) return t('when.justNow');
+	if (seconds < 3600) return t('when.minutes', { n: Math.floor(seconds / 60) });
+	if (seconds < 86400) return t('when.hours', { n: Math.floor(seconds / 3600) });
+	if (seconds < 604800) return t('when.days', { n: Math.floor(seconds / 86400) });
+	return then.toLocaleDateString(tag(), { day: 'numeric', month: 'short', year: 'numeric' });
+}
+
+/** A date and a time, for a list where the time of day matters. */
+export function stamp(iso) {
+	return new Date(iso).toLocaleString(tag(), {
+		day: 'numeric',
+		month: 'short',
+		hour: '2-digit',
+		minute: '2-digit'
+	});
+}
+
+/** A day, without the year — for something inside the next few months. */
+export function shortDate(iso) {
+	return new Date(iso).toLocaleDateString(tag(), { day: 'numeric', month: 'short' });
+}
+
+/** A day with the year, for something that could be any distance away. */
+export function fullDate(iso) {
+	return new Date(iso).toLocaleDateString(tag(), {
+		day: 'numeric',
+		month: 'short',
+		year: 'numeric'
+	});
+}