Add integration test verifying multi-token decimal handling end-to-end

[Marvell69]

Description
Given USDC/EURC (6 decimals) vs. XLM (7 decimals) handling is a documented cross-cutting concern in the broader project, and the frontend has real components for token selection/display, an end-to-end test confirming correct decimal handling across the actual submission → display → funding flow (not just isolated unit tests of the formatting utility) would catch integration-level regressions unit tests alone might miss.

Requirements and context

• Write a Playwright E2E test submitting an invoice in XLM, confirming the amount displays correctly formatted (7 decimals) throughout the submission, marketplace listing, and funding confirmation steps
• Repeat for a 6-decimal token to confirm no cross-contamination of formatting logic
• Add to e2e-tests.yml

Suggested execution

git checkout -b test/e2e-multi-token-decimal-handling

• Write E2E test covering XLM and USDC/EURC decimal display through the full flow
• Wire into E2E CI

Example commit message
test: add E2E coverage for multi-token decimal handling across full flow

[Meme11030]

@Meme11030 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

hi maintainer i will like to work on this issue please

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Meme11030 to this issue.