feat(sprint9): Phase 2 — Financial report generators (EÜR, Kassenbuch, Beitragsbescheinigung)

Implements Sprint 9 Phase 2 financial report generators:

- MemberReportParameters: new parameter record for per-member reports
- EurReportGenerator: Einnahmen-Überschuss-Rechnung (§4(3) EStG)
  - PDF: professional layout with income/expense sections, monthly breakdown
  - CSV: semicolon-delimited, ISO-8859-1, German decimal format
  - JSON: ELSTER-compatible structure for Steuerberater import
- KassenbuchExportGenerator: GoBD-compliant cash book export
  - PDF: landscape A4, running balance, sequential Beleg-Nr
  - CSV: GoBD-compliant format with injection prevention
  - Includes opening balance calculation and period totals
- BeitragsbescheinigungGenerator: membership fee confirmation per member
  - PDF: club letterhead, payment table, signature lines
  - For member tax purposes (Sonderausgaben)
- ReportGeneratorService: added getAvailableTypes() method
- ReportController: added GET /api/v1/reports/types endpoint

All generators are @Service beans auto-discovered by ReportGeneratorService.
Docker build verified green.

cannamanage-api/src/main/java/de/cannamanage/api/controller/ReportController.java

@@ -5,9 +5,12 @@ import de.cannamanage.api.dto.report.MonthlyReportResponse;
 import de.cannamanage.api.dto.report.RecallReportResponse;
 import de.cannamanage.domain.entity.Club;
 import de.cannamanage.domain.entity.TenantContext;
+import de.cannamanage.domain.enums.ExportFormat;
 import de.cannamanage.domain.enums.MemberStatus;
+import de.cannamanage.domain.enums.ReportType;
 import de.cannamanage.service.CsvReportGenerator;
 import de.cannamanage.service.PdfReportGenerator;
+import de.cannamanage.service.ReportGeneratorService;
 import de.cannamanage.service.ReportService;
 import de.cannamanage.service.model.report.MemberListReport;
 import de.cannamanage.service.model.report.MonthlyReport;
@@ -20,7 +23,7 @@ import org.springframework.security.access.prepost.PreAuthorize;
 import org.springframework.web.bind.annotation.*;
 
 import java.time.YearMonth;
-import java.util.UUID;
+import java.util.*;
 
 /**
  * REST controller for compliance and operational reports.
@@ -34,15 +37,41 @@ public class ReportController {
     private final PdfReportGenerator pdfGenerator;
     private final CsvReportGenerator csvGenerator;
     private final ClubRepository clubRepository;
+    private final ReportGeneratorService reportGeneratorService;
 
     public ReportController(ReportService reportService,
                             PdfReportGenerator pdfGenerator,
                             CsvReportGenerator csvGenerator,
-                            ClubRepository clubRepository) {
+                            ClubRepository clubRepository,
+                            ReportGeneratorService reportGeneratorService) {
         this.reportService = reportService;
         this.pdfGenerator = pdfGenerator;
         this.csvGenerator = csvGenerator;
         this.clubRepository = clubRepository;
+        this.reportGeneratorService = reportGeneratorService;
+    }
+
+    /**
+     * List all available report types with their supported export formats.
+     * GET /api/v1/reports/types
+     */
+    @GetMapping("/types")
+    @PreAuthorize("hasRole('ADMIN') or @staffPermissions.has(#root, T(de.cannamanage.domain.enums.StaffPermission).VIEW_COMPLIANCE_REPORT)")
+    public ResponseEntity<List<Map<String, Object>>> listReportTypes() {
+        Map<ReportType, Set<ExportFormat>> availableTypes = reportGeneratorService.getAvailableTypes();
+
+        List<Map<String, Object>> response = new ArrayList<>();
+        for (var entry : availableTypes.entrySet()) {
+            Map<String, Object> typeInfo = new LinkedHashMap<>();
+            typeInfo.put("type", entry.getKey().name());
+            typeInfo.put("formats", entry.getValue().stream()
+                    .map(ExportFormat::name)
+                    .sorted()
+                    .toList());
+            response.add(typeInfo);
+        }
+
+        return ResponseEntity.ok(response);
     }
 
     /**