feat(train): each km announced on foot, each 5 km by bike (ADR 0030, D49)

Step 11 takes up what OpenTracks does that Train didn't (D49). 11a: a
recording announces each kilometre on foot and each 5 km by bike, never
on a rower, where the Record sheet's switch is on for the activity
(remembered in the person's announce.json, off at first): the distance,
the moving time, the split's pace or speed and the heart rate. The app
hands the recorder the words in its language; Announcer.kt counts the
moving time and the distance, Cues.kt speaks the line after a cue still
speaking.

Not tried on a phone yet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/train/halkyon_train_flutter/lib/l10n/app_de.arb

@@ -505,5 +505,14 @@
   "recordMusic": "Musik",
   "recordMusicOn": "Musik",
   "recordMetronome": "Metronom",
-  "recordMusicOff": "Aus"
+  "recordMusicOff": "Aus",
+  "recordAnnounce": "Ansagen",
+  "recordAnnounceFoot": "Jeden Kilometer: Zeit, Pace und Puls",
+  "recordAnnounceBike": "Alle 5 km: Zeit, Tempo und Puls",
+  "announceKilometres": "{count, plural, =1{1 Kilometer} other{{count} Kilometer}}",
+  "announceHours": "{count, plural, =1{1 Stunde} other{{count} Stunden}}",
+  "announceTime": "Zeit {time}",
+  "announcePace": "Pace {pace} pro Kilometer",
+  "announceSpeed": "Tempo {speed} Kilometer pro Stunde",
+  "announceHeartRate": "Puls {bpm}"
 }