Handle/show warning when CSV data is missing File Path column

## Description

Encountered by @MFarhadloo25. Majid was having an issue where a CSV would load into CFE but clicking on the 3D view for any cell would just show a black screen.

On closer investigation, the `File Path` column was missing from Majid's data, as he had defined the URL in the `Link Path` column instead.

## Expected Behavior

- CFE should use the URL in the `Link Path` if no `File Path` column is defined.
- CFE should show a warning that there is no `File Path` provided in the 3D view tab when there is no URL.

## Reproduction

1. Download this CSV: [bad.csv](https://github.com/user-attachments/files/26310817/embeddings_val_sub_structure.csv)
2. Open https://cfe.allencell.org
3. Click load and drop in the CSV.
4. Click on any cell, then view it in the 3D view.
5. The 3D view will be black.

Repeat the steps with a fixed CSV that includes a File Path:
[fixed.csv](https://github.com/user-attachments/files/26310840/embeddings_val_sub_structure.csv)

## Environment

_Any additional information about your environment. E.g. OS version, python version, browser etc._