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/model/report/report.go

@@ -47,6 +47,13 @@ type Report struct {
 	OtherGroup         []OtherGroup         `json:"otherGroup,omitempty"`
 	UnidentifiedGroup  []UnidentifiedGroup  `json:"unidentifiedGroup,omitempty"`
 
+	// Race exit warnings. PersonalExitWarning is the recipient race's own
+	// number of turns remaining before auto-removal for inactivity (set when
+	// it is 1..5, otherwise 0). RacesLeavingSoon lists other races within 3
+	// turns of removal and is shown to every recipient.
+	PersonalExitWarning uint             `json:"personalExitWarning,omitempty"`
+	RacesLeavingSoon    []RaceExitNotice `json:"racesLeavingSoon,omitempty"`
+
 	OnPlanetGroupCache     map[uint][]int           `json:"-"`
 	InSpaceGroupRangeCache map[int]map[uint]float64 `json:"-"`
 }
@@ -71,6 +78,13 @@ type Player struct {
 	Extinct    bool      `json:"extinct"`
 }
 
+// RaceExitNotice is a public notice that a race is within a few turns of being
+// auto-removed for inactivity; TurnsLeft is the number of turns until removal.
+type RaceExitNotice struct {
+	Race      string `json:"race"`
+	TurnsLeft uint   `json:"turnsLeft"`
+}
+
 func (r Report) MarshalBinary() (data []byte, err error) {
 	return json.Marshal(&r)
 }