Fix/multi issue 568 569 570 571

[Joycejay17]

Description

Four small, independent fixes across contracts and frontend: a duplicate doc comment, two accessibility gaps, and a duplicate utility function.

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• 🔧 Refactoring (no functional changes)

Related Issues

Closes #568 , Closes #569 , Closes #570 , Closes #571

Changes Made

#568 — contracts/stream_contract/src/events.rs

• Removed the redundant first line (/// Emitted when a stream is paused.) from the StreamPausedEvent doc comment, keeping the more precise second line (/// Emitted when a sender pauses an active stream.).

#569 — frontend/src/components/ui/Button.tsx

• Added aria-busy={loading} to the <button> element so screen readers announce the in-progress state.
• Marked the spinner SVG aria-hidden="true" to suppress its meaningless announcement.
• Added a <span className="sr-only">Loading</span> alongside the spinner so assistive technology reads a meaningful label when loading is true.

#570 — frontend/src/components/dashboard/StreamDetailsModal.tsx

• Guarded the progress calculation: deposited > 0 ? Math.min(100, Math.max(0, (withdrawn / deposited) * 100)) : 0 — was NaN/Infinity when deposited === 0.
• Added aria-label="Close" to the × close button, consistent with other modals in the app.

#571 — frontend/src/components/TransactionTracker.tsx

• Imported formatAmount from the shared @/utils/amount utility.
• Deleted the private formatAmount(raw, decimals) at the bottom of the file. The local copy used BigInt(10 ** decimals) which is fragile for decimals > 15; the shared util uses the safe 10n ** BigInt(decimals) form.

Testing

Test Coverage

• Manual testing performed

Test Steps

#568

1. cd contracts && cargo build — confirms the contract still compiles cleanly.

#569

1. Trigger any loading button (create stream, withdraw, top-up, cancel).
2. Inspect with browser DevTools: aria-busy="true" present on <button>, spinner has aria-hidden="true", and a .sr-only "Loading" span is in the DOM.
3. Use VoiceOver / NVDA — "Loading" is announced when the button enters loading state.

#570

1. Open Stream Details for a stream with deposited === 0 — progress bar renders at 0% (was broken/NaN width).
2. Confirm the × button is announced as "Close" by a screen reader.

#571

1. Trigger a transaction and let it reach the confirmed state — the "Summary of Changes" section renders amounts correctly.
2. cd frontend && npm run build — no TypeScript errors in TransactionTracker.tsx.

Screenshots/Demo

No visual regression — the spinner appearance, modal layout, and transaction tracker UI are unchanged.

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my own code
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published
• I have checked for breaking changes and documented them if applicable

Additional Notes

• Issue [Frontend] TransactionTracker re-implements formatAmount locally — use shared util #571 defers to whichever path the lib/amount vs utils/amount consolidation ([Frontend] Consolidate duplicate amount helpers in lib/amount.ts and utils/amount.ts #520) settles on; @/utils/amount was chosen as it is the more complete file and is already used by the majority of components and the test suite.
• The Tailwind bg-gradient-to-br → bg-linear-to-br IDE suggestion in StreamDetailsModal.tsx is a pre-existing lint suggestion unrelated to this PR and is left untouched per the "out of scope" constraint.