refactor(ui): web/admin amber->main 치환 + theme.ts deprecated 별칭 제거 (WS-AMBER)

- apps/web 11건 + apps/admin 10건 accent.amber->main 치환
- packages/ui/src/theme.ts에서 amber/amberDim/amberGlow @deprecated 별칭 제거
  (본체 main/dim/glow 유지). 전 모노레포 amber 잔여 0건 확인.
SKIP: site/src/tokens.ts(별도 토큰 계통, d3roPalette 비의존)
정책: docs/REFACTOR_POLICY.md DP1, 이식 인사이트 P7

apps/web/src/app/(app)/billing/page.tsx

@@ -93,7 +93,7 @@ export default async function BillingPage(): Promise<React.ReactElement> {
                   p: 4,
                   height: '100%',
                   border: active
-                    ? `2px solid ${d3roPalette.accent.amber}`
+                    ? `2px solid ${d3roPalette.accent.main}`
                     : plan.highlight
                       ? `2px solid ${d3roPalette.tag.purple}`
                       : undefined,
@@ -124,7 +124,7 @@ export default async function BillingPage(): Promise<React.ReactElement> {
                       p: 1.5,
                       bgcolor: d3roPalette.bg.inset,
                       borderRadius: 1,
-                      color: d3roPalette.accent.amber,
+                      color: d3roPalette.accent.main,
                       ...typoSx('label'),
                     }}
                   >

apps/web/src/app/(app)/meetings/[id]/page.tsx

@@ -111,7 +111,7 @@ export default async function MeetingDetailPage({ params }: PageProps): Promise<
                     key={memo.id}
                     sx={{
                       p: 1.5,
-                      borderLeft: `3px solid ${d3roPalette.accent.amber}`,
+                      borderLeft: `3px solid ${d3roPalette.accent.main}`,
                       bgcolor: d3roPalette.bg.inset
                     }}
                   >