Fix contribution compounding: monthly contributions are now added to
asset values before each GBM step so they grow with market returns,
rather than being summed as a static lump at each period.
Add year-by-year milestone table below the fan chart showing P10/P50/P90
portfolio values at each annual checkpoint up to the selected horizon.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>