ENH: Refactor snapshot list and add admin edit dialog

[tiffany-slac]

Description

Key changes include renaming the comment field to description, updating UI elements for clarity, and adding an editable dialog for admins to modify snapshot titles and descriptions. The snapshot list now updates immediately when edits are saved.

• Renamed all instances of 'comment' to 'description' for code consistency with backend
• Updated snapshot title color from primary to text.primary to avoid link-like appearance
• Added overflow handling to PV checkbox to remove the dot in Chrome
• Removed severity column
• Added admin edit ability for snapshots with a dialog to edit title/description, consistent with Tag Group edit UI/UX
• Ensured snapshot list updates immediately after dialog closes
• Added updateSnapshot method to snapshotService

Motivation

• Backend uses description instead of comment; frontend changes maintain consistency.
• Blue, bold snapshot titles looked like clickable links; color update improves readability.
• Chrome rendered a dot in the PV checkbox due to overflow; fixed for cross-browser consistency.
• Remove the severity column (Closes Remove defunct status indicator column #12).
• Admins need the ability to edit snapshots easily; the new dialog matches existing Tag Group edit UX (Closes Enable editing snapshot titles and descriptions #33).

Screenshots

Admin Edit Icon

Edit Dialog

Removed Severity column

Dot in Chrome

Pre-merge checklist

• Code works interactively
• Code follows the style guide
• Code contains descriptive docstrings
• New/changed functions and methods are covered in the test suite where possible
• Test suite passes locally
• Test suite passes on GitHub Actions