feat: daily scenario generation scheduling at midnight KST

[Copilot]

Implements automated daily scenario generation triggered at 00:00 KST: requests AI server generation, polls for completion, generates images, and assigns the result as the next day's scenario — with up to 5 retries on any failure.

Key changes

• @EnableScheduling added to MainServerApplication
• ScenarioDailyScheduler (new component):
  • Fires at 0 0 0 * * * Asia/Seoul via @Scheduled; launches work in a non-blocking CoroutineScope(Dispatchers.IO + SupervisorJob())
  • Also triggers once on server startup via @EventListener(ApplicationReadyEvent::class)
  • Skips generation if a scenario for tomorrow already exists (ScenarioRepository.findByDate check) — prevents duplicate generation on midnight cron or server restart
  • Target date (now + 1 day) captured once before the retry loop — consistent across all attempts regardless of execution duration
  • Polls AiClient.getScenarioCreateTask(key) every 30 s; hard cap of 240 polls (2 h) prevents unbounded execution
  • On COMPLETED: runs ImageGenerationService.generateImagesForScenario → AdminService.updateScenarioDate(tomorrow)
  • On FAILED, poll timeout, or any exception: returns false → outer loop retries up to 5 times

@EventListener(ApplicationReadyEvent::class)
fun onApplicationReady() {
    scope.launch { generateScenarioWithRetry() }
}

@Scheduled(cron = "0 0 0 * * *", zone = "Asia/Seoul")
fun scheduleScenarioGeneration() {
    scope.launch { generateScenarioWithRetry() }
}

• ScenarioDailySchedulerTest — 8 unit tests using runTest (virtual time; no real 30 s waits) covering: skip when tomorrow's scenario exists, happy path, retry-then-succeed, max retries exhausted, startGeneration throws, null scenarioId, poll timeout, and poll exception recovery

Original prompt

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This section details on the original issue you should resolve

<issue_title>시나리오 생성 scheduling</issue_title>
<issue_description>## 기능 요구 사항

• 매일 00시에 시나리오 생성을 시작한다.
  • ai 서버에 생성 요청
  • task 30초마다 polling을 해서 생성이 끝났는지 확인
  • 이미지 생성
  • 성공적으로 생성시 다음날 시나리오로 지정
  • 실패시 처음부터 최대 5회 다시 시작</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes 시나리오 생성 scheduling #40

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[dev-yunseong]

@copilot
그리고 서버 켰을 때도 한번 생성을 시도하도록 해줘

[dev-yunseong]

@copilot 내일 날짜로 이미 시나리오가 있으면 생성을 스킵하는 기능도 만들어줘

[Copilot]

@copilot
그리고 서버 켰을 때도 한번 생성을 시도하도록 해줘

Added in d06da9e via @EventListener(ApplicationReadyEvent::class). It calls the same generateScenarioWithRetry(), so the "already exists" check prevents a double-generation if the server restarts after midnight has already run.