Feat: add image preview to retrieval test. (#7610)

### What problem does this PR solve?

#7608

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

rag/app/picture.py

@@ -36,7 +36,8 @@ def chunk(filename, binary, tenant_id, lang, callback=None, **kwargs):
     doc = {
         "docnm_kwd": filename,
         "title_tks": rag_tokenizer.tokenize(re.sub(r"\.[a-zA-Z]+$", "", filename)),
-        "image": img
+        "image": img,
+        "doc_type_kwd": "image"
     }
     bxs = ocr(np.array(img))
     txt = "\n".join([t[0] for _, t in bxs if t[0]])