Error handling added to MVP according to error_handling.md guideline

tests/services/test_upload.py

@@ -16,7 +16,7 @@ class TestUploadValidation:
     def test_rejects_empty_bytes(self, session, tmp_path: Path):
         """create_upload_job rejects an empty upload payload."""
         settings = Settings(openrouter_api_key="test-key", upload_dir=tmp_path)
-        with pytest.raises(UploadError):
+        with pytest.raises(UploadError) as exc_info:
             create_upload_job(
                 filename="letter.jpg",
                 file_bytes=b"",
@@ -24,10 +24,13 @@ class TestUploadValidation:
                 settings=settings,
             )
 
+        assert exc_info.value.category.value == "validation_error"
+        assert "non-empty" in exc_info.value.suggestion.lower()
+
     def test_rejects_unsupported_extension(self, session, tmp_path: Path):
         """create_upload_job rejects unsupported filename extensions."""
         settings = Settings(openrouter_api_key="test-key", upload_dir=tmp_path)
-        with pytest.raises(UploadError):
+        with pytest.raises(UploadError) as exc_info:
             create_upload_job(
                 filename="notes.txt",
                 file_bytes=b"content",
@@ -35,6 +38,9 @@ class TestUploadValidation:
                 settings=settings,
             )
 
+        assert exc_info.value.category.value == "user_input_error"
+        assert "jpg" in exc_info.value.suggestion.lower()
+
 
 @pytest.mark.integration
 class TestUploadPersistence: