feat: improve workspace actions and delete confirmation on dashboard

[neethika12]

Why this change

The dashboard used a browser-native confirm popup for workspace deletion and had limited inline feedback, which made deletion feel abrupt and less reliable to users.

What changed

• Replaced the browser confirm dialog with an in-app confirmation modal for deleting a workspace
• Added inline success and error feedback messages after delete actions
• Added in-progress delete state so users see when deletion is happening
• Kept the workspace action row consistent by showing Edit with Open and Delete
• Updated dashboard copy to include JIRA in the signals overview text

User impact

• Workspace deletion is now clearer, safer, and visually consistent with the app
• Users get immediate confirmation when deletion succeeds or fails
• Action buttons on workspace cards are more predictable and easier to scan

Validation

• npm test -- --watch=false --browsers=ChromeHeadless (all tests passing)