Fix feedback attachments: proper MIME mixed/alternative structure

Rewrite feedback.py with correct MIMEMultipart(mixed) containing
alternative text part + base64-encoded image attachments.

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

src/routers/feedback.py

@@ -39,7 +39,6 @@ _user_timestamps: dict[int, list[float]] = defaultdict(list)
 _MAX_PER_HOUR = 3
 _WINDOW = 3600
 
-
 _ALLOWED_TYPES = {"image/jpeg", "image/png"}
 _MAX_FILE_SIZE = 5 * 1024 * 1024  # 5 MB
 _MAX_FILES = 3
@@ -105,16 +104,32 @@ async def send_feedback(
   </div>
 </div>"""
 
-    msg = MIMEMultipart("alternative")
+    msg = MIMEMultipart("mixed")
     msg["From"] = f"{SMTP_FROM_NAME} <{SMTP_FROM_EMAIL}>"
     msg["To"] = FEEDBACK_EMAIL
     msg["Subject"] = subject
     if email:
         msg["Reply-To"] = email
 
+    # Text-Teil (alternative: plain + html)
+    text_part = MIMEMultipart("alternative")
     text_fallback = f"Feedback von {display_name} ({category_label}):\n\n{message}"
-    msg.attach(MIMEText(text_fallback, "plain", "utf-8"))
+    text_part.attach(MIMEText(text_fallback, "plain", "utf-8"))
-    msg.attach(MIMEText(html_body, "html", "utf-8"))
+    text_part.attach(MIMEText(html_body, "html", "utf-8"))
+    msg.attach(text_part)
+
+    # Bild-Anhaenge
+    for f in files:
+        file_data = await f.read()
+        if len(file_data) > _MAX_FILE_SIZE:
+            raise HTTPException(status_code=422, detail=f"Datei {f.filename} ist groesser als 5 MB.")
+        sub_type = (f.content_type or "image/jpeg").split("/")[1]
+        attachment = MIMEBase("image", sub_type)
+        attachment.set_payload(file_data)
+        encoders.encode_base64(attachment)
+        attachment.add_header("Content-Disposition", "attachment", filename=f.filename or "bild.jpg")
+        msg.attach(attachment)
+        logger.debug(f"Anhang: {f.filename} ({len(file_data)} Bytes, {f.content_type})")
 
     try:
         await aiosmtplib.send(
@@ -126,7 +141,7 @@ async def send_feedback(
             start_tls=SMTP_USE_TLS,
         )
         _user_timestamps[user_id].append(now)
-        logger.info(f"Feedback von {display_name} ({category_label}) gesendet")
+        logger.info(f"Feedback von {display_name} ({category_label}) gesendet, {len(files)} Anhaenge")
     except Exception as e:
         logger.error(f"Feedback-E-Mail fehlgeschlagen: {e}")
         raise HTTPException(