feat: enhance user API key management and implement soft delete

- Redirect users to API Keys tab after login instead of overview
- Remove Token Limit and Daily Cost Limit from user API key details modal
- Implement soft delete for API keys to preserve usage statistics
- Add admin endpoint to view deleted API keys with metadata
- Track deletion metadata (deletedBy, deletedAt, deletedByType)
- Ensure deleted API keys cannot be restored
- Include deleted key stats in user totals while excluding from active count

🤖 Generated with [Claude Code](https://claude.ai/code)

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

web/admin-spa/src/views/UserDashboardView.vue

@@ -282,7 +282,7 @@ import UserUsageStats from '@/components/user/UserUsageStats.vue'
 const router = useRouter()
 const userStore = useUserStore()
 
-const activeTab = ref('overview')
+const activeTab = ref('api-keys')
 const userProfile = ref(null)
 
 const formatNumber = (num) => {