feat(game): race exit warnings in the turn report (#12)

Surface the inactivity-removal countdown the rules promise but the
engine never reported. A race within five turns of being auto-removed
for inactivity gets a personal warning in its own report; every race
within three turns is listed publicly to all participants.

- model: Report.PersonalExitWarning + RacesLeavingSoon ([]RaceExitNotice)
- fbs: RaceExitNotice table + Report.personal_exit_warning /
  races_leaving_soon (regenerated Go + TS bindings)
- transcoder: encode/decode both fields
- engine: ReportExitWarnings fills the recipient's TTL (1..5) and lists
  other non-extinct races with TTL 1..3, excluding the recipient itself
- ui: danger-styled personal banner + "races leaving soon" section
  (hidden when empty), wired into the report view, EN/RU i18n
- docs: rules.txt report-section list, FUNCTIONAL.md 6.4 + RU mirror

Voluntary quit and idle timeout share the TTL countdown and are not
distinguished, per the agreed scope.

pkg/transcoder/report_test.go

@@ -365,6 +365,11 @@ func sampleReport() *model.Report {
 		UnidentifiedGroup: []model.UnidentifiedGroup{
 			{X: model.Float(10.0), Y: model.Float(11.0)},
 		},
+		PersonalExitWarning: 4,
+		RacesLeavingSoon: []model.RaceExitNotice{
+			{Race: "Martians", TurnsLeft: 2},
+			{Race: "Klingons", TurnsLeft: 1},
+		},
 		OnPlanetGroupCache: map[uint][]int{
 			1: {2, 3},
 		},