Add a locale-aware relative-time helper; drop stale locale overrides

Node.recently_changed and the new dashboard need "X ago" rendered
correctly in both locales. Rails' own distance_of_time_in_words/
time_ago_in_words can't do this on their own -- the scope option
changes which translation key is looked up, not the underlying
grammar, and German's "vor" requires dative case, which is a
different word form than the nominative plural Rails computes by
default. relative_time_phrase/relative_distance is a small, from-
scratch bucketing helper instead, with an explicit, hand-checked
translation table per unit per locale.

Also removes de.yml's datetime.distance_in_words and activerecord.
errors blocks. Both used the old {{count}}/{{model}} interpolation
syntax the current i18n gem no longer recognizes -- it silently
leaves the literal placeholder text in the rendered output rather
than erroring, which is why this went unnoticed until now. Both were
shadowing rails-i18n's own current, correct translations for exactly
these keys; deleting the local override lets the gem's version take
over instead of maintaining a second, broken copy.

1 files changed, 19 insertions, 0 deletions

diff --git a/test/models/helpers/datetime_helper_test.rb b/test/models/helpers/datetime_helper_test.rb
new file mode 100644
index 0000000..a24e5d3
--- /dev/null
+++ b/test/models/helpers/datetime_helper_test.rb
@@ -0,0 +1,19 @@
+require 'test_helper'
+
+class DatetimeHelperTest < ActionView::TestCase
+  test "relative_time_phrase pluralizes correctly in English and German" do
+    travel_to Time.zone.parse("2026-07-12 12:00:00") do
+      I18n.with_locale(:en) do
+        assert_equal "1 day ago", relative_time_phrase(1.day.ago)
+        assert_equal "3 days ago", relative_time_phrase(3.days.ago)
+      end
+      I18n.with_locale(:de) do
+        assert_equal "vor 1 Tag", relative_time_phrase(1.day.ago)
+        assert_equal "vor 3 Tagen", relative_time_phrase(3.days.ago)
+        assert_equal "vor 1 Monat", relative_time_phrase(30.days.ago)
+        assert_equal "vor 2 Monaten", relative_time_phrase(45.days.ago)
+        assert_equal "vor 2 Jahren", relative_time_phrase(2.years.ago)
+      end
+    end
+  end
+end