## Description
Previously, a user with no per-user override and no membership in a budgeted group had no effective group, so their AI spend was attributed nowhere and was, therefore, untracked. This change falls back to the organization's Everyone group when no override or group budget applies.
Since every user in an organization is implicitly a member of that org's Everyone group, spend is now attributed and tracked for any user with organization membership. A user with no organization membership resolves to no group, so their daily spend is not incremented and a warning is logged.
The fallback is unlimited, so enforcement is unaffected: only override and group budgets can block requests. For users in multiple organizations, an existing budget on any Everyone group is still chosen by the "highest" policy; when none is budgeted, the fallback prefers the default org, then orders by organization name.
## Changes
- Add `ResolveUserEffectiveGroup` and the `GetUserEveryoneFallbackGroup` query: resolve override → group budget → Everyone group fallback.
- Attribute token-usage spend and the user AI spend endpoint via the fallback, so unbudgeted users resolve to their Everyone group instead of null.
- Update `GetGroupMembersAISpend` to surface the Everyone fallback as the effective group.
- Update `GetHighestGroupAIBudgetByUser` to break ties by organization name then group name, keeping multi-org resolution deterministic and consistent with the fallback.
- For multi-org users with no budget anywhere, the fallback picks the Everyone group deterministically: prefer the default org, then order by organization name.
Closes https://linear.app/codercom/issue/AIGOV-509/fall-back-to-the-everyone-group-for-spend-attribution
> [!NOTE]
> Initially generated by Claude Opus 4.7, modified and reviewed by @ssncferreira
Susana Ferreira
c23f2c0223