Docs updates for E/A#98500 full beneficial owner SSN and CAD bank statement

[MelvinBot]

Explanation of Change

Help site updates for the behavior changed by #98500 ([Payment due @getusha] Add bank statement and ssn requirements). That PR made three user-visible changes that the existing articles either contradicted or did not describe:

1. Beneficial owners now give a full nine-digit SSN, not the last four. The UBO SSN sub-step switched from isValidSSNLastFour to isValidSSNFullNine, and the input label changed from Last 4 of SSN to Full 9 digits of SSN. This affects both the USD business bank account flow and the non-USD global reimbursement flow, and it applies whenever a beneficial owner's country of citizenship is the United States. The signer's own personal details still ask for the last four digits, so that copy was deliberately left alone.
2. CAD accounts must now upload a bank statement on the Agreements screen. isBankStatementNeeded expanded from AUD only to AUD and CAD, and getStartPageForContinueSetup sends you back to Agreements if you try to resume at the Docusign step without one. The same upload field was also added to the Enable Global Reimbursements flow for USD bank accounts, where it did not exist before.
3. Canada's proof of beneficial owner requirement changed. Canadian accounts are now asked for Schedule 50 (Shareholder Information) from the most recent T2 corporate income tax return, instead of the signed attestation and org chart from a public accountant, notary, or lawyer.

Files changed:

• docs/articles/new-expensify/wallet-and-payments/Connect-a-Business-Bank-Account.md — documents the beneficial owner fields and states that the full SSN is required, and calls out that this differs from the last-four-digit ask in your own personal details.
• docs/articles/new-expensify/wallet-and-payments/Global-Reimbursement-Canada.md — adds SSN to the beneficial owner field list, replaces the attestation/org chart requirement with Schedule 50, and adds a new section for the Agreements screen and its bank statement upload.
• docs/articles/new-expensify/wallet-and-payments/Global-Reimbursement-United-States.md — moves the bank statement upload to where it actually appears (the Agreements screen) and notes that the ACH authorization form is gated behind it.
• docs/articles/new-expensify/wallet-and-payments/Global-Reimbursement-United-Kingdom.md — corrects SSN only if based in the US, which is now wrong on both the amount asked for and the condition that triggers it.

UI labels used in the copy (Full 9 digits of SSN, Bank statement, Choose file, Accept and add bank account, Proof of beneficial owner, Agreements) were taken from the merged strings in src/languages/en.ts and the components that render them. A browser walk of the CAD setup flow was attempted to confirm them on screen, but it was blocked by the email security-code screen on Connect manually, so the labels are verified against the merged source rather than a live screenshot. Please confirm them against the real flow.

Two things intentionally left out of scope:

• The # Step N: headings in the United States article do not meet the current heading rules in docs/HELP_AUTHORING_GUIDELINES.md (one # per article, task-based headings). Rewriting them would touch sections this PR has no reason to change, so they were left as-is.
• The Expensify Classic global reimbursement articles describe the older Classic setup path and were not touched.

cspell could not be run in this environment, so spelling was not machine-verified.

Fixed Issues

$ https://github.com/Expensify/Expensify/issues/649256
PROPOSAL:

Tests

// TODO: The human co-author must fill out the tests you ran before marking this PR as "ready for review"
// Please describe what tests you performed that validates your changed worked.

• Verify that no errors appear in the JS console

Offline tests

QA Steps

// TODO: These must be filled out, or the issue title must include "[No QA]."
// TODO: The human co-author must fill out the QA tests you ran before marking this PR as "ready for review".
// Please describe what QA needs to do to validate your changes and what areas do they need to test for regressions.

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
  • I verified that comments were added to code that is not self explanatory
  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I followed the guidelines as stated in the Review Guidelines
• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
• If a new CSS style is added I verified that:
  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG))
• If new assets were added or existing ones were modified, I verified that:
  • The assets are optimized and compressed (for SVG files, run npm run compress-svg)
  • The assets load correctly across all supported platforms.
• If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• I added unit tests for any new feature or bug fix in this PR to help automatically prevent regressions in this user flow.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.

Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

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@madmax330, please review the files changed and confirm they reflect the current behavior. Then post a new comment saying @MelvinBot mark this PR as ready for review.