Fix up "Manage team" page UI

[vdavid]

@rrhyne left a bunch of feedback in this figma and this Loom that I totally overlooked at first.

This PR contains all the fixes listen in the Figma and Loom (unless I mixed something).

This is a complete list:

• Page
  • Added missing page title
  • Removed "open in new" icon from "Manage subscription" link
  • Made the "Add seats" button be of the "success" type (green) rather than "primary" (blue)
• Invites
  • Fixed textarea label copy
  • Added a red outline to textbox if the input has an error
  • Made the error text replace the help text in case of an error
  • Left-aligned "Send" button
• Team member list
  • Converted the list to a table-like arrangement
  • Updated "Re-send invite" button type to "secondary" (outline)
  • Center-aligned action buttons
  • Fix copy: "Resend" → "Re-send" to match the figma

Also:

• Code cleanup: Removed an unneeded condition) – see separate commit
• Use text-uppercase class in ADMIN and INVITED labels

Test plan

Here is a 2.5-minute Loom where I demo the changes.

[taras-yemets]

Why do we need these empty divs?

[vdavid]

Because the grid layout needs five columns. If I don't include the empty divs, the layout gets messed up. Tried it.

[taras-yemets]

Approving to unblock. Left a few minor comments inline.