fix(frontend): auto-refresh relative dates as time passes

Relative dates ("5 minutes ago", "in 2 hours") were computed once via
dayjs().fromNow() and never recomputed, so a view left open kept showing
the value from the moment it was rendered.

Compute the relative string against the shared, ticking `now` from
useGlobalNow() instead. This makes every reactive caller — <TimeDisplay>,
direct formatDateSince() calls, and formatDisplayDate() when the user's
date display is set to relative — re-render on the existing 60s tick.
Absolute date formats don't read `now`, so they never needlessly
re-render.

useGlobalNow can now be initialised from a plain helper rather than only
from a component, so its route-update hook is guarded with
getCurrentInstance().

frontend/src/composables/useGlobalNow.ts

@@ -1,4 +1,4 @@
-import { ref } from 'vue'
+import { getCurrentInstance, ref } from 'vue'
 import { createGlobalState, useIntervalFn } from '@vueuse/core'
 import { onBeforeRouteUpdate } from 'vue-router'
 
@@ -18,10 +18,14 @@ export const useGlobalNow = createGlobalState(() => {
 
 	useIntervalFn(update, GLOBAL_NOW_INTERVAL, { immediate: true })
 
-	// ensure the now value is refreshed when the route changes
+	// Now that this state can be initialised from a plain helper (formatDateSince), the
-	onBeforeRouteUpdate(() => {
+	// first caller is not guaranteed to be a component — guard the route hook accordingly.
-		update()
+	if (getCurrentInstance()) {
-	})
+		// ensure the now value is refreshed when the route changes
+		onBeforeRouteUpdate(() => {
+			update()
+		})
+	}
 
 	return {
 		now,

frontend/src/helpers/time/formatDate.ts

@@ -5,6 +5,7 @@ import {i18n} from '@/i18n'
 import {createSharedComposable} from '@vueuse/core'
 import {computed, toValue, type MaybeRefOrGetter} from 'vue'
 import {useDateDisplay} from '@/composables/useDateDisplay'
+import {useGlobalNow} from '@/composables/useGlobalNow'
 import {useTimeFormat} from '@/composables/useTimeFormat'
 import {DATE_DISPLAY, type DateDisplay} from '@/constants/dateDisplay'
 import {TIME_FORMAT, type TimeFormat} from '@/constants/timeFormat'
@@ -49,8 +50,13 @@ export const formatDateSince = (date: Date | string | null) => {
 
 	const locale = DAYJS_LOCALE_MAPPING[i18n.global.locale.value.toLowerCase()] ?? 'en'
 
+	// Computing the relative string against the shared, ticking `now` (instead of fromNow's
+	// internal Date.now()) makes every reactive caller re-render on the 60s tick, so open views
+	// don't keep showing a stale "x minutes ago".
+	const {now} = useGlobalNow()
+
 	return date
-		? dayjs(date).locale(locale).fromNow()
+		? dayjs(date).locale(locale).from(now.value)
 		: ''
 }