Adds the current user's AI spend progress to the top navbar avatar
dropdown when /api/v2/users/me/ai/spend reports a configured spend
limit. The shared dropdown content accepts an optional profileExtra
slot so the Agents sidebar can opt in later without changing the
default sidebar UI.
Introduces a temporary site API type and a React Query helper for
AIGOV-473 that refetches each time the dropdown opens, plus shared
budget progress helpers used by both the new dropdown bar and the
existing Agents usage indicator. The shared AIBudgetUsage component
moves to site/src/components so the dropdown and group budget UI
format spend identically, including the unlimited case. The avatar
border polls the spend endpoint and is colored by severity while the
dropdown is closed.
Closes AIGOV-473
Ehab Younes
6b297912a5