Fix the remaining type errors in src/

- Declare the --ig-fill custom property on React's CSSProperties once,
  instead of casting the style prop in Footer, Home and EventList-Cards.
- Type Footer's Get_In_Touch links as internal or external, so the
  external branch type-checks.
- Pass undefined rather than null for an absent gradient (Home) and
  Instagram URL (EventList-Cards).

tsc --noEmit is now clean, with and without --noImplicitAny.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/components/Footer.tsx

@@ -39,7 +39,13 @@ const Social_Links = [
 // Only the label differs down here.
 const giveAction = NAV_ACTIONS.find((a) => a.variant === "fancy");
 
-const Get_In_Touch = [
+/* An internal route, or an off-site address opened in a new tab. */
+type TouchLink = { label: string } & (
+  | { external?: false; to: string }
+  | { external: true; href: string }
+);
+
+const Get_In_Touch: TouchLink[] = [
   { label: "Feedback",   to: "/feedback"},
   { label: "Contact Us", to: "/leadership#contact" },
 ];