Add API endpoint to check staff application availability and enforce open/close periods

backend/src/main/java/com/alttd/altitudeweb/controllers/forms/ApplicationController.java

@@ -16,9 +16,12 @@ import com.alttd.altitudeweb.services.mail.StaffApplicationMail;
 import com.alttd.altitudeweb.setup.Connection;
 import lombok.AllArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.HttpStatusCode;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.RestController;
 
+import java.time.Instant;
 import java.util.Optional;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
@@ -34,8 +37,24 @@ public class ApplicationController implements ApplicationsApi {
     private final StaffApplicationMail staffApplicationMail;
     private final StaffApplicationDiscord staffApplicationDiscord;
 
+    private final Instant open = Instant.parse("2025-10-18T00:00:00Z");
+    private final Instant close = Instant.parse("2020-10-26T00:00:00Z");
+
+    @Override
+    public ResponseEntity<Boolean> getStaffApplicationsIsOpen() {
+        return ResponseEntity.ok(isOpen());
+    }
+
+    private boolean isOpen() {
+        Instant now = Instant.now();
+        return !now.isBefore(open) && !now.isAfter(close);
+    }
+
     @Override
     public ResponseEntity<FormResponseDto> submitStaffApplication(StaffApplicationDto staffApplicationDto) {
+        if (!isOpen()) {
+            return ResponseEntity.status(HttpStatus.FORBIDDEN).build();
+        }
         UUID userUuid = AuthenticatedUuid.getAuthenticatedUserUuid();
 
         String email = staffApplicationDto.getEmail() == null ? null : staffApplicationDto.getEmail().toLowerCase();