[Feature] Add a new column that shows the data size of the atlas in the Atlas Manager."

**Is your feature request related to a problem? Please describe.**
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When downloading atlases, I sometimes look for ones with a smaller data size so that the download finishes faster. However, I have difficulty determining which atlas will finish downloading more quickly.

**Describe the solution you'd like**
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Add a new column called `data size` to the Atlas Manager view.

**Describe alternatives you've considered**
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Append the data size to the atlas name (e.g., `Columbia cuttlefile (50μm) 14.0MB`).

Start with the Atlas Manager view and trace how atlas metadata and download information are loaded. Add a data size column, or use the proposed name suffix alternative, and verify that each listed atlas shows its size consistently.

Written by the indexing model from the issue text.