refactor(claude): drop the redundant Team-tab account budget (T-158)

After live review: the shared account /usage budget read as redundant on
both the Activity and Team tabs. Usage is per-account and can't be split per
member, so one place is enough — it lives only on the Activity tab, next to
the refresh control that fetches it (T-415). Removes the Team-tab account
card, its usage prop wiring, the team.section.usage/team.usage.shared i18n
keys, and the now-obsolete team_tab test. The three-tab card facelift stays.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

assets/i18n/en_us/builtin.claude.json

@@ -194,8 +194,6 @@
   "taskRow.reassign": { "translation": "Reassign task" },
   "team.empty": { "translation": "No team active." },
   "team.section.tasks": { "translation": "TASKS" },
-  "team.section.usage": { "translation": "Account" },
-  "team.usage.shared": { "translation": "Shared across the team" },
   "tabStrip.activity": { "translation": "Activity" },
   "tabStrip.team": { "translation": "Team" },
   "tabStrip.team.count": { "translation": "Team · {count}" },

assets/i18n/nl_nl/builtin.claude.json

@@ -194,8 +194,6 @@
   "taskRow.reassign": { "translation": "Taak opnieuw toewijzen" },
   "team.empty": { "translation": "Geen team actief." },
   "team.section.tasks": { "translation": "TAKEN" },
-  "team.section.usage": { "translation": "Account" },
-  "team.usage.shared": { "translation": "Gedeeld met het hele team" },
   "tabStrip.activity": { "translation": "Activiteit" },
   "tabStrip.team": { "translation": "Team" },
   "tabStrip.team.count": { "translation": "Team · {count}" },