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.

ui/frontend/tests/e2e/report-sections.spec.ts

@@ -45,6 +45,7 @@ const BATTLE_ID = "00000000-0000-0000-0000-000000000001";
 // the popover and a `report-section-<slug>` testid in the body.
 const SECTIONS: ReadonlyArray<{ slug: string; expectRow: string | null }> = [
 	{ slug: "galaxy-summary", expectRow: "galaxy-summary-field-turn" },
+	{ slug: "race-exit-warnings", expectRow: "race-exit-warnings-row" },
 	{ slug: "votes", expectRow: "votes-mine" },
 	{ slug: "player-status", expectRow: "player-status-row" },
 	{ slug: "my-sciences", expectRow: "my-sciences-row" },
@@ -161,6 +162,10 @@ async function mockGateway(page: Page): Promise<void> {
 						shipProductions: [
 							{ planet: 1, class: "Cruiser", cost: 100, prodUsed: 25, percent: 0.25, free: 800 },
 						],
+						racesLeavingSoon: [
+							{ race: "Bajori", turnsLeft: 2 },
+							{ race: "Cardassian", turnsLeft: 3 },
+						],
 					});
 					break;
 				}