Tree cards: render unset-sex / redacted "Living person" in gray, not blue

The chart mapped gender as `=== "female" ? "F" : "M"`, so anything non-female —
including null — became "M" (blue). On the public site, redacted living people
(whose gender the privacy engine nulls) all showed blue regardless of real sex,
and anywhere a person's sex was simply unset they also showed blue (misleading).

Map male→"M", female→"F", and everything else→null, which family-chart renders
as `card-genderless`. So living/redacted people render gray (and never imply a
sex), and unset-sex people render gray instead of defaulting to male/blue.
Applied to both the member tree (tree/page.tsx) and the public chart
(public-tree-chart.tsx), which share chart.css. Also bumped the genderless color
from the library's washed-out `lightgray` to a warm mid-gray that matches the
muted male/female tones and the brand palette.

Privacy note: `_redact` already nulls gender, so this is purely the client color
mapping — no sex leak, just a correct neutral rendering.

Signed-off-by: Justin Paul <justin@jpaul.me>

frontend/components/public-tree-chart.tsx

@@ -120,7 +120,10 @@ export function PublicTreeChart({
             "first name": fn || "Unnamed",
             "last name": ln,
             birthday: years.get(pp.id) ?? "",
-            gender: pp.gender === "female" ? "F" : "M",
+            // male → blue, female → pink, unset/redacted → genderless (gray).
+            // Redacted living people have null gender, so they render gray rather
+            // than defaulting to male/blue (and never imply a real person's sex).
+            gender: pp.gender === "male" ? "M" : pp.gender === "female" ? "F" : null,
           },
           rels: {
             spouses: ok(partnersOf(pp.id), pp.id),