feat(desktop): SaaS [6] 로컬 우선 sync + login_required UI (빅뱅 Phase 3)

Phase 3 재정의: Supabase = source of truth 방향 철회.
로컬 entry point 철학 하에 "로컬이 SoT, 클라우드는 로그인 시 mirror"로 확정.

CloudSyncService._initialSync():
- _onAuthenticated 끝에 fire-and-forget 호출
- pushAll → pullAll 순차 실행
- signin: 익명 로컬 데이터를 사용자 계정으로 업로드
- restore: 다른 기기 변경 반영
- 실패 시 warn만, 수동 Sync 버튼으로 재시도 가능

types.ts:
- FeatureAccess.reason: 'login_required' 추가
- UpgradePromptEvent.reason: 'login_required' 추가

LicenseService:
- consumeQuota(): login_required 케이스 — promptUpgrade + D3ROError(TierRequired)
- promptUpgrade(): login_required 시 requiredTier='free'
  (로그인만 하면 free로 바로 사용 가능)
- quota_exceeded 시 현재 tier 상위로 승격 제안

UpgradePromptModal:
- isLoginRequired 분기 — title/desc 교체
- Primary button: "로그인하기" → d3ro:open-settings event (tab=cloud)

i18n ko/en:
- license.loginRequired.title/desc/signIn 추가

apps/desktop/src/renderer/components/UpgradePromptModal.tsx

@@ -44,9 +44,15 @@ export function UpgradePromptModal(): React.ReactElement {
   if (!event) return <></>
 
   const isQuota = event.reason === 'quota_exceeded'
+  const isLoginRequired = event.reason === 'login_required'
   const featureLabel = t(`license.feature.${event.feature}`)
   const tierLabel = event.requiredTier === 'pro_plus' ? t('license.proPlus') : t('license.pro')
 
+  const openCloudSyncSettings = (): void => {
+    setOpen(false)
+    window.dispatchEvent(new CustomEvent('d3ro:open-settings', { detail: { tab: 'cloud' } }))
+  }
+
   return (
     <Dialog
       open={open}
@@ -77,7 +83,9 @@ export function UpgradePromptModal(): React.ReactElement {
         <LockIcon sx={{ fontSize: 20 }} />
         {isQuota
           ? t('license.quotaExceeded.title', { feature: featureLabel })
-          : t('license.tierRequired.title', { feature: featureLabel, tier: tierLabel })}
+          : isLoginRequired
+            ? t('license.loginRequired.title', { feature: featureLabel })
+            : t('license.tierRequired.title', { feature: featureLabel, tier: tierLabel })}
       </DialogTitle>
 
       <DialogContent>
@@ -91,7 +99,9 @@ export function UpgradePromptModal(): React.ReactElement {
         >
           {isQuota
             ? t('license.quotaExceeded.desc')
-            : t('license.tierRequired.desc', { tier: tierLabel })}
+            : isLoginRequired
+              ? t('license.loginRequired.desc')
+              : t('license.tierRequired.desc', { tier: tierLabel })}
         </Typography>
 
         {/* 쿼터 바 */}
@@ -155,7 +165,7 @@ export function UpgradePromptModal(): React.ReactElement {
         </Button>
         <Button
           variant="contained"
-          onClick={handleLearnMore}
+          onClick={isLoginRequired ? openCloudSyncSettings : handleLearnMore}
           sx={{
             fontFamily: d3roFontMono,
             fontSize: d3roTypo.compact.size,
@@ -170,7 +180,7 @@ export function UpgradePromptModal(): React.ReactElement {
             },
           }}
         >
-          {t('license.learnMore')}
+          {isLoginRequired ? t('license.loginRequired.signIn') : t('license.learnMore')}
         </Button>
       </DialogActions>
     </Dialog>