feat: add import status tracking to MassImportService

The async import previously ran fire-and-forget with no way to know
if it succeeded, failed, or was still running.

- Add ImportStatus record (state, message, processed count, startedAt)
  and a volatile currentStatus field updated throughout the async run
- POST /api/admin/trigger-import now returns 202 Accepted with initial status
- GET /api/admin/import-status lets callers poll for the current state

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/controller/AdminController.java

@@ -4,6 +4,7 @@ import org.raddatz.familienarchiv.security.Permission;
 import org.raddatz.familienarchiv.security.RequirePermission;
 import org.raddatz.familienarchiv.service.MassImportService;
 import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
@@ -19,8 +20,13 @@ public class AdminController {
     private final MassImportService massImportService;
 
     @PostMapping("/trigger-import")
-    public ResponseEntity<String> triggerMassImport() {
+    public ResponseEntity<MassImportService.ImportStatus> triggerMassImport() {
         massImportService.runImportAsync();
-        return ResponseEntity.ok("Massenimport gestartet.");
+        return ResponseEntity.accepted().body(massImportService.getStatus());
+    }
+
+    @GetMapping("/import-status")
+    public ResponseEntity<MassImportService.ImportStatus> importStatus() {
+        return ResponseEntity.ok(massImportService.getStatus());
     }
 }

backend/src/main/java/org/raddatz/familienarchiv/service/MassImportService.java

@@ -22,6 +22,7 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.time.LocalDate;
+import java.time.LocalDateTime;
 import java.time.ZoneId;
 import java.util.Optional;
 import java.util.UUID;
@@ -32,6 +33,16 @@ import java.util.stream.Stream;
 @Slf4j
 public class MassImportService {
 
+    public enum State { IDLE, RUNNING, DONE, FAILED }
+
+    public record ImportStatus(State state, String message, int processed, LocalDateTime startedAt) {}
+
+    private volatile ImportStatus currentStatus = new ImportStatus(State.IDLE, "Kein Import gestartet.", 0, null);
+
+    public ImportStatus getStatus() {
+        return currentStatus;
+    }
+
     private final DocumentRepository documentRepository;
     private final S3Client s3Client;
 
@@ -52,23 +63,15 @@ public class MassImportService {
 
     @Async
     public void runImportAsync() {
-        runImport();
+        currentStatus = new ImportStatus(State.RUNNING, "Import läuft...", 0, LocalDateTime.now());
-    }
-
-    public String runImport() {
         try {
-            // 1. Excel finden
             File excelFile = findExcelFile();
             log.info("Starte Massenimport aus: {}", excelFile.getAbsolutePath());
-
-            // 2. Excel verarbeiten
             int processed = processExcel(excelFile);
-
+            currentStatus = new ImportStatus(State.DONE, "Import abgeschlossen. " + processed + " Dokumente verarbeitet.", processed, currentStatus.startedAt());
-            return "Import abgeschlossen. " + processed + " Dokumente verarbeitet.";
-
         } catch (Exception e) {
             log.error("Massenimport fehlgeschlagen", e);
-            return "Fehler: " + e.getMessage();
+            currentStatus = new ImportStatus(State.FAILED, "Fehler: " + e.getMessage(), 0, currentStatus.startedAt());
         }
     }