fix: bigger water-taxi boat marker + darker unread notification tint

[fatherlinux]

Summary

Two small UI tweaks requested by Scott:

• Water-taxi boat marker 30% bigger — createBoatIcon SVG 20×32 → 26×42, iconSize/iconAnchor scaled to match. Easier to spot on the map.
• Unread notification tint darkened — .notification-item.unread background #f3f8ee → #dcebc6. The old near-white tint was hard to distinguish from read items against the white panel.

Test plan

• GHA build green
• Boat marker visibly larger on the map (live water-taxi tracker)
• Unread notifications clearly tinted vs read ones

[gemini-code-assist]

Code Review

This pull request updates the background color of unread notification items in App.css and increases the dimensions of the boat icon SVG and Leaflet marker configuration in Map.jsx. A review comment identifies an accessibility issue where the new background color results in insufficient contrast with the metadata text, and suggests darkening the text color specifically for unread notifications to meet WCAG 2.1 Level AA standards.

[gemini-code-assist]

The new background color #dcebc6 for unread notifications combined with the meta text color #777 (defined in .notification-meta) results in a contrast ratio of approximately 3.6:1. This falls below the WCAG 2.1 Level AA minimum contrast requirement of 4.5:1 for normal text, which may make timestamps and other metadata difficult to read for users with visual impairments.

To resolve this while keeping the darker background, we can darken the meta text color specifically for unread notification items to #555 (which yields a contrast ratio of 6.0:1).

.notification-item.unread {
  background: #dcebc6;
}
.notification-item.unread .notification-meta {
  color: #555;
}