Implement backup and restore functionality; add IBackupService and BackupService; refactor services to use DbContextFactory

src/Duempelkas.Infrastructure/Services/PdfStatementService.cs

@@ -12,15 +12,15 @@ namespace Duempelkas.Infrastructure.Services;
 
 public class PdfStatementService : IPdfStatementService
 {
-    private readonly FinanceDbContext _db;
+    private readonly IDbContextFactory<FinanceDbContext> _dbFactory;
     private readonly IEntryService _entryService;
     private readonly IBalanceQueryService _balanceQueryService;
     private readonly ISettingsService _settingsService;
     private static readonly CultureInfo DeLocale = new("de-DE");
 
-    public PdfStatementService(FinanceDbContext db, IEntryService entryService, IBalanceQueryService balanceQueryService, ISettingsService settingsService)
+    public PdfStatementService(IDbContextFactory<FinanceDbContext> dbFactory, IEntryService entryService, IBalanceQueryService balanceQueryService, ISettingsService settingsService)
     {
-        _db = db;
+        _dbFactory = dbFactory;
         _entryService = entryService;
         _balanceQueryService = balanceQueryService;
         _settingsService = settingsService;
@@ -28,7 +28,9 @@ public class PdfStatementService : IPdfStatementService
 
     public async Task<byte[]> GenerateStatementAsync(int accountId, bool currentYearOnly)
     {
-        var account = await _db.Accounts.FindAsync(accountId)
+        await using var db = await _dbFactory.CreateDbContextAsync();
+
+        var account = await db.Accounts.FindAsync(accountId)
             ?? throw new InvalidOperationException($"Konto {accountId} nicht gefunden.");
 
         var entries = await _entryService.GetEntriesAsync(accountId, currentYearOnly);