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/test/support/fake_recorder_platform.dart

@@ -31,6 +31,7 @@ class FakeRecorderPlatform({
           Map<String, Object?>? plan,
           Map<String, Object?>? route,
           Map<String, Object?>? music,
+          Map<String, Object?>? announce,
         })
       >[];
 
@@ -86,6 +87,7 @@ class FakeRecorderPlatform({
     Map<String, Object?>? plan,
     Map<String, Object?>? route,
     Map<String, Object?>? music,
+    Map<String, Object?>? announce,
   }) async {
     started.add((
       path: path,
@@ -97,6 +99,7 @@ class FakeRecorderPlatform({
       plan: plan,
       route: route,
       music: music,
+      announce: announce,
     ));
     notices.add(notice);
     _file = File(path)