feat: google drive internal formats support

[mateuszkuprowski]

This implementation replaces the older approach using the Google Drive API's
`files.export()` and `files.get_media()` methods, which were limited by export size
restrictions (~10MB hard cap for Google-native files).

**New mechanism:**
- Authenticates using a service account and generates a bearer token via `google-auth`.
- Uses `files().get(fileId=..., fields="exportLinks,webContentLink")` to fetch download URLs:
    - `exportLinks` is a dictionary of export MIME types (e.g., docx, pdf, pptx) for
      Google-native files like Docs, Sheets, and Slides.
    - `webContentLink` is a pre-authenticated direct download link for non-Google-native
      files (e.g., PDFs, images, ZIPs, etc.).
      
These links emulate the behavior of Google Drive's "File > Download as..." options
in the UI and bypass the size limitations of `files.export()`.

 **Behavior:**
- Google-native formats are downloaded using `exportLinks` in appropriate MIME formats.
- Binary files (non-Google-native) are downloaded using `webContentLink`.
- All downloads are performed via `requests.get()` using a valid bearer token.

[pawel-kmiecik]

LGTM!

[bryan-unstructured]

well, this is not related to your PR, but I find a previously existing bug :-) Can you please also update it?
between Line 444 - 447

def extract_permissions(self, permissions: Optional[list[dict]]) -> list[dict]:
        if not permissions:
            logger.debug("no permissions found")
            return {}

should return [{}], otherwise would cause error in some cases.
Overall the PR looks good to me!