Add RRULE humanizer and wire events into nodes#showerdgeist-revive-events

- app/models/concerns/rrule_humanizer.rb: new concern included into
  Event, renders recurring schedule as natural-language German or
  English from RRULE string; handles WEEKLY/MONTHLY, biweekly
  (INTERVAL=2), ordinal weekday positions (1TU, -1TH, -2WE),
  BYMONTH single-month exclusions (December pause convention);
  gracefully returns nil for COUNT/UNTIL/unrecognized shapes
- test/models/concerns/rrule_humanizer_test.rb: 15 tests covering
  all distinct RRULE shapes found in production data
- app/helpers/nodes_helper.rb: add event_schedule_text helper
  combining humanize_rrule with start_time formatting
- app/views/nodes/show.html.erb: add events row, conditionally
  rendered when node has associated events
- config/locales/de.yml, en.yml: add event_schedule_time,
  event_schedule_unrecognized, event_schedule_none keys

1 files changed, 3 insertions, 0 deletions

diff --git a/config/locales/de.yml b/config/locales/de.yml
index 5f77d79..0b42dd3 100644
--- a/config/locales/de.yml
+++ b/config/locales/de.yml
@@ -7,6 +7,9 @@ de:
   sponsors: Sponsoren
   show_tag_headline: "Seiten mit dem Tag:"
   old_ccc_de: das alte ccc.de
+  event_schedule_time: "um %{time} Uhr"
+  event_schedule_unrecognized: "Termin-Regel nicht automatisch lesbar"
+  event_schedule_none: "Kein Termin"
   date:
     formats:
       default: "%d.%m.%Y"