feat(frontend): add quick runway preset buttons (+7, +30, +90 days) to TopUpModal

[aazminu]

Description

Adds quick runway preset pill buttons (+7 Days, +30 Days, +90 Days) and a projected end date preview to TopUpModal (frontend/src/components/stream-creation/TopUpModal.tsx).

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔧 Refactoring (no functional changes)
• ⚡ Performance improvement
• 🧪 Test addition or update

Related Issues

Closes #1635
Fixes #1635
/claim #1635

Changes Made

• Added and exported calculateRunwayPresetAmount, calculateProjectedEndDate, and formatProjectedEndDate in frontend/src/components/stream-creation/TopUpModal.tsx.
• Rendered +7 Days, +30 Days, and +90 Days quick-fill preset buttons (role="group", aria-label="Quick runway presets") that calculate ratePerSecond * 86400 * days (capped to 7 Stellar decimals) and populate the top-up amount field.
• Rendered the projected end date (data-testid="projected-end-date") in the preview section when a valid top-up amount and stream rate are present, and passed ratePerSecond={modal.stream.ratePerSecond} from frontend/src/components/dashboard/dashboard-view.tsx.
• Added unit tests in frontend/src/components/stream-creation/__tests__/TopUpModal.test.tsx verifying preset button clicks (+7 Days, +30 Days, +90 Days), projected end date rendering, and helper edge cases.

Testing

Test Coverage

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed

Test Steps

1. Run npx vitest run src/components/stream-creation/__tests__/TopUpModal.test.tsx src/__tests__/a11y.test.tsx src/components/dashboard/dashboard-view.test.tsx in frontend/ (18/18 tests pass).
2. Run npx tsc --noEmit in frontend/ (0 errors).
3. Run npx eslint src/components/stream-creation/TopUpModal.tsx src/components/stream-creation/__tests__/TopUpModal.test.tsx in frontend/ (0 errors, 0 warnings).

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have checked for breaking changes and documented them if applicable

Additional Notes

Payout Details

• USDT/USDC Receiving Wallet (EVM / ERC-20 / Polygon / Arbitrum / Optimism / Base / BSC): 0x9a51790aC01c54184bcFa067bC38f7F0E7C6F6B6