Handle Edge Cases in Dataset Preprocessing and Query Validation

[sahithi-66]

• Throw an error if the dataset_name already exists before starting the preprocessing step. This will prevent accidental overwrites or conflicts.
• Ensure that the dataset_name is saved only if the preprocessing step completes successfully. This will prevent partial or failed datasets from being saved.
• Fix the code to process images located within subdirectories of the dataset directory. Currently, only files in the root directory are processed.
• Implement a validation to check whether the input file is a valid image file before processing. This ensures only image files are processed, avoiding errors with invalid file types.
• Check whether the input directory is empty before proceeding with preprocessing. If the directory is empty, return an appropriate error message.
• Ensure that the text query input is neither empty nor None. If it is, throw an error or prompt the user to provide valid input.
• Update the code to automatically trim leading and trailing spaces from the dataset_name input provided by the user. This ensures consistency and prevents errors caused by unintended spaces in dataset names during processing or database operations.