feat(avatar): understand BOXIM image messages

digital-avatar-app/backend/routers/chat.py

@@ -236,11 +236,40 @@ async def _analyze_uploaded_image(
     max_bytes = max(1024, int(os.getenv("CHAT_IMAGE_MAX_BYTES", str(8 * 1024 * 1024))))
     content = await file.read(max_bytes + 1)
     filename = os.path.basename(file.filename or "图片")[:255]
+    try:
+        return _analyze_image_bytes(
+            db,
+            avatar,
+            content,
+            filename=filename,
+            mime_type=file.content_type or "",
+            uploader_kind=uploader_kind,
+        )
+    except ImageValidationError as exc:
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
+    except InsufficientTokensError:
+        raise
+    except RuntimeError as exc:
+        raise HTTPException(status_code=502, detail=str(exc)) from exc
+    finally:
+        content = b""
+
+
+def _analyze_image_bytes(
+    db: Session,
+    avatar: Avatar,
+    content: bytes,
+    *,
+    filename: str,
+    mime_type: str,
+    uploader_kind: str,
+) -> ChatAttachment:
+    """Analyze image bytes from either HTTP upload or BOXIM without persisting raw data."""
     attachment = ChatAttachment(
         avatar_id=avatar.id,
         uploader_kind=uploader_kind,
         filename=filename,
-        mime_type=(file.content_type or "")[:100],
+        mime_type=(mime_type or "")[:100],
         file_size=len(content),
         status="processing",
         expires_at=_attachment_expiry(),
@@ -312,7 +341,7 @@ async def _analyze_uploaded_image(
         attachment.status = "failed"
         attachment.warning = str(exc)
         db.commit()
-        raise HTTPException(status_code=400, detail=str(exc)) from exc
+        raise
     except InsufficientTokensError:
         attachment.status = "failed"
         attachment.warning = "积分余额不足"
@@ -328,9 +357,7 @@ async def _analyze_uploaded_image(
             avatar.id,
             type(exc).__name__,
         )
-        raise HTTPException(status_code=502, detail=str(exc)) from exc
-    finally:
-        content = b""
+        raise
 
 
 def _normalize_question(value: str) -> str: