fix(can-funding): serialize pending actions to preserve history ordering

[johndeange]

What changed

Replaces the parallel Promise.allSettled save strategy in CanFunding.hooks.js with a sequential pendingActions queue that dispatches mutations in the exact order the user took them in the UI. This fixes issue #5571, where budget and funding-received mutations raced on the client, causing the backend to record history events in non-deterministic order.

frontend/src/pages/cans/detail/CanFunding.hooks.js

• Added PendingAction type and exported mergePendingAction utility that collapses redundant queue entries (e.g., repeated budget edits, edit-then-delete of a staged row)
• Added pendingActions state; handleAddBudget, handleAddFundingReceived, and deleteFundingReceived now enqueue typed actions
• Rewrote saveChanges to iterate the queue sequentially with a for...of / switch dispatch, preserving user-intended ordering

frontend/src/pages/cans/detail/CanFunding.hooks.test.js

• Fixed mock setup to use .unwrap() pattern matching the new sequential calls
• Added tests: mutation call ordering, queue collapsing for repeated edits, and staged add+delete cancellation

frontend/cypress/e2e/canFundingHistoryOrdering.cy.js (new)

• E2E regression test: enters FY Budget then Funding Received, saves, and asserts the history panel shows them in correct newest-first order

frontend/cypress.config.js / cypress.config.ci.js

• Registered the new E2E spec in the ordered spec lists

Issue

#5571

How to test

Unit tests:

cd frontend && bun run test -- --watch=false src/pages/cans/detail/CanFunding.hooks.test.js

E2E test (requires Docker stack running):

cd frontend && bun run test:e2e -- --spec cypress/e2e/canFundingHistoryOrdering.cy.js

Manual verification:

1. Log in as a budget-team user
2. Navigate to a CAN's Funding tab for the current fiscal year
3. Click Edit, enter an FY Budget amount, click "Add FY Budget"
4. Enter a Funding Received amount + notes, click "Add Funding Received"
5. Click Save — observe network tab shows budget request completing before received request fires
6. Navigate to the CAN's history panel — "Funding Received Added" should appear above the FY Budget entry

A11y impact

• No accessibility-impacting changes in this PR

Screenshots

N/A — no visual changes; behavior fix only affects mutation ordering and history display sequence.

Definition of Done Checklist

• OESA: Code refactored for clarity
• Automated unit tests updated and passed
• Automated integration tests updated and passed
• Automated quality tests updated and passed
• Automated load tests updated and passed
• Automated a11y tests updated and passed
• Automated security tests updated and passed
• 90%+ Code coverage achieved
• Form validations updated

Links

N/A