feat(tickets): Foto-/Datei-Anhänge an Tickets

- Anhänge im Melde-Fenster (beim Erstellen) und direkt an bestehenden Tickets:
  Vorschaubilder, Öffnen im neuen Tab, Entfernen.
- Bytes liegen in eigener Tabelle (FeedbackAttachment, lose FeedbackId ohne FK →
  übersteht den Ingest-Wipe); GET /feedback liefert nur Metadaten (id/Name/Typ/Größe),
  die Bytes über /feedback/attachments/{id}. Größenlimit 10 MB.
- Endpoints: POST /feedback/{id}/attachments (base64), GET /feedback/attachments/{id}
  (Bytes), DELETE /feedback/attachments/{id}.

Migration FeedbackAttachments. Tests: 262 Backend grün (+Upload/Serve/Delete +Validierung),
e2e Tickets Desktop+Phone grün (+Foto-Upload), vitest 149.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

GerbilManagerWebAPI/Dtos/FeedbackDtos.cs

@@ -20,6 +20,19 @@ namespace GerbilManagerWebAPI.Dtos
         string Text,
         DateTimeOffset? At);
 
+    /// <summary>FEEDBACK: lightweight metadata for an attachment (no bytes).</summary>
+    public record FeedbackAttachmentDto(
+        Guid Id,
+        string FileName,
+        string ContentType,
+        int Size);
+
+    /// <summary>FEEDBACK: payload to upload an attachment (base64-encoded bytes).</summary>
+    public record FeedbackAttachmentInput(
+        string FileName,
+        string ContentType,
+        string DataBase64);
+
     /// <summary>FEEDBACK: response DTO for a stored report.</summary>
     public record FeedbackDto(
         Guid Id,
@@ -51,7 +64,9 @@ namespace GerbilManagerWebAPI.Dtos
         /// <summary>Optional AI-set category/topic for filtering (e.g. "Genetik", "Import"); null = none.</summary>
         string? Category = null,
         /// <summary>Was the resolution helpful? true=👍, false=👎, null=no feedback yet.</summary>
-        bool? Helpful = null);
+        bool? Helpful = null,
+        /// <summary>Attachment metadata (no bytes); fetch bytes via /feedback/attachments/{id}.</summary>
+        IReadOnlyList<FeedbackAttachmentDto>? Attachments = null);
 
     /// <summary>
     /// FEEDBACK: payload for PUT /feedback/{id}. Edit the message and/or toggle status,