phase 8: lobby UI + cross-stack lobby command catalog + TS FlatBuffers

- Extend pkg/model/lobby and pkg/schema/fbs/lobby.fbs with public-games
  list, my-applications/invites lists, game-create, application-submit,
  invite-redeem/decline. Mirror the matching transcoder pairs and Go
  fixture round-trip tests.
- Wire the seven new lobby message types through
  gateway/internal/backendclient/{routes,lobby_commands}.go with
  per-command REST helpers, JSON-tolerant decoding of backend wire
  shapes, and httptest-based unit coverage for success / 4xx / 5xx /
  503 across each command.
- Introduce TS-side FlatBuffers via the `flatbuffers` runtime dep, a
  `make fbs-ts` target driving flatc, and the generated bindings under
  ui/frontend/src/proto/galaxy/fbs. Phase 7's `user.account.get` decode
  now uses these bindings as well, closing the JSON.parse vs
  FlatBuffers gap that would have failed against a real local stack.
- Replace the placeholder lobby with five sections (my games, pending
  invitations, my applications, public games, create new game) and the
  /lobby/create form. Submit-application uses an inline race-name
  form on the public-game card; create-game keeps name / description /
  turn_schedule / enrollment_ends_at always visible and the rest under
  an Advanced toggle with TS-side defaults.
- Update lobby/+page.svelte to throw LobbyError on non-ok result codes;
  GalaxyClient.executeCommand now returns { resultCode, payloadBytes }.
- Vitest binding round-trips, lobby.ts wrapper unit tests, lobby-page
  + lobby-create component tests, Playwright lobby-flow.spec covering
  create / submit / accept across all four projects. Phase 7 e2e was
  migrated to the FlatBuffers fixtures and to click+fill against the
  Safari-autofill readonly inputs.
- Mark Phase 8 done in ui/PLAN.md, mirror the wire-format note into
  Phase 7, append the new lobby commands to gateway/README.md and
  docs/ARCHITECTURE.md, add ui/docs/lobby.md.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ui/frontend/src/lib/i18n/locales/en.ts

@@ -35,6 +35,53 @@ const en = {
 	"lobby.greeting": "hello, {name}!",
 	"lobby.account_loading": "loading account…",
 	"lobby.logout": "logout",
+	"lobby.section.my_games": "my games",
+	"lobby.section.invitations": "pending invitations",
+	"lobby.section.applications": "my applications",
+	"lobby.section.public_games": "public games",
+	"lobby.section.create": "create a game",
+	"lobby.create_button": "create new game",
+	"lobby.my_games.empty": "no games yet",
+	"lobby.invitations.empty": "no invitations",
+	"lobby.applications.empty": "no applications",
+	"lobby.public_games.empty": "no public games",
+	"lobby.invitation.accept": "accept",
+	"lobby.invitation.decline": "decline",
+	"lobby.application.submit": "submit application",
+	"lobby.application.submit_for": "join {name}",
+	"lobby.application.race_name_label": "race name",
+	"lobby.application.race_name_required": "race name must not be empty",
+	"lobby.application.cancel": "cancel",
+	"lobby.application.submitted": "application submitted, awaiting approval",
+	"lobby.application.status.pending": "pending",
+	"lobby.application.status.approved": "approved",
+	"lobby.application.status.rejected": "rejected",
+	"lobby.application.status.unknown": "{status}",
+	"lobby.list_loading": "loading…",
+	"lobby.create.title": "create new game",
+	"lobby.create.game_name_label": "game name",
+	"lobby.create.description_label": "description",
+	"lobby.create.turn_schedule_label": "turn schedule",
+	"lobby.create.turn_schedule_hint": "five-field cron, e.g. 0 0 * * *",
+	"lobby.create.enrollment_ends_at_label": "enrollment ends at",
+	"lobby.create.advanced": "advanced",
+	"lobby.create.min_players_label": "min players",
+	"lobby.create.max_players_label": "max players",
+	"lobby.create.start_gap_hours_label": "start gap (hours)",
+	"lobby.create.start_gap_players_label": "start gap (players)",
+	"lobby.create.target_engine_version_label": "target engine version",
+	"lobby.create.submit": "create",
+	"lobby.create.submitting": "creating…",
+	"lobby.create.cancel": "cancel",
+	"lobby.create.game_name_required": "game name must not be empty",
+	"lobby.create.turn_schedule_required": "turn schedule must not be empty",
+	"lobby.create.enrollment_ends_at_required": "enrollment end time must be set",
+	"lobby.error.invalid_request": "request is invalid",
+	"lobby.error.subject_not_found": "not found",
+	"lobby.error.forbidden": "operation is forbidden",
+	"lobby.error.conflict": "request conflicts with current state",
+	"lobby.error.internal_error": "internal server error",
+	"lobby.error.unknown": "{message}",
 } as const;
 
 export default en;