MPDX-10092 Check staffAccountId before showing the PGA balance card

[jbirdjavi]

Description

• To decide whether to show the balance card, Partner Giving Analysis ran the StaffAccount query. For a user with a staff account id, the API answers that with a full, unfiltered SAA account summary (one of SAA's most expensive calls) on every page load, only to read the id. (Users without one never reached SAA; the resolver returns nil first.) The card then runs its own FundBalances summary anyway.
• The report now decides with the existing StaffAccountId query (user.staffAccountId, a plain MPDX read with no SAA call). That saves one SAA account summary per page load for staff.
• BalanceCard never leaves its skeleton up once loading ends:
  • It renders nothing when FundBalances fails. That case used to stay hidden because StaffAccount failed first for a user whose staff account SAA does not know. Now such a user passes the id check, so the card has to handle the failure itself. The same single "SAA Error" snackbar shows as before.
  • It renders nothing when the query succeeds with no Primary fund (an older bug, found in review).
• Also fixed, found in review: when the period had no gifts, {donationPeriodTotalSum && ...} printed a bare "0" (the field is Int!) and hid the total. The card now shows "Total Donations for this period $0.00".
• Tests: the report shows the card without running StaffAccount, and hides it (with no FundBalances call) when staffAccountId is null. The card renders nothing on a query error or with no Primary fund, and shows a zero total. All five fail on main.
• A local /code-review at xhigh (fresh Opus agent) found no regressions. It traced impersonation, users with no staff account, an id SAA doesn't know, and loading through both versions.

Jira ticket: MPDX-10092
API side of the same ticket: https://github.com/CruGlobal/mpdx_api/pull/3680 (independent; either can ship first)

Testing

• Sign in as a user with a staff account and go to Reports > Partner Giving Analysis.
• Check that the Primary Account Balance card still shows.
• In the browser's network tab, check that the page sends StaffAccountId and FundBalances, and no StaffAccount operation.
• Sign in as (or impersonate) a user without a staff account, such as a non-Cru user. Check that no balance card shows and no FundBalances request is sent.
• Pick a filter period with no gifts. Check that the card shows "Total Donations for this period" with $0.00, not a stray "0".

Checklist:

• I have given my PR a title with the format "MPDX-(JIRA#) (summary sentence max 80 chars)"
• I have applied the appropriate labels (Add the label "Preview" to automatically create a preview environment)
• I have run the Claude Code /quality:agent-review command locally and fixed any relevant suggestions
• I have requested a review from another person on the project
• I have tested my changes in preview or in staging
• I have cleaned up my commit history

🤖 Generated with Claude Code

[github-actions]

Bundle sizes [mpdx-react]

Compared against 8cef3e7

No significant changes found

[dr-bizz]

I'm so glad you found this and are fixing it. I don't think the person who added it knew that it would cost SAA as much as it did.