Type src/ against API and database shapes, fixing implicit anys

Adds .d.ts declarations beside the untyped JS modules imported from
TS (api.js, navConfig.js, adminSchema.js, adminNav.js, src/data/*),
with shapes taken from the server routes and migrations. get/post/
patch/del now return unknown unless the caller names the response.

Fixes found along the way:
- website/email/instagram are bare strings from splitLinks, not Link
  objects; OrganizationDetail's website and email pills rendered with
  no href or label and now link correctly.
- The chapter map falls back to FALLBACK_COLOR for a region with no
  colour instead of painting its tiles black.

Adds defineSection() so each page manifest entry's props are checked
against its own Component.

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

src/components/ArrowLink.tsx

@@ -4,7 +4,15 @@ import { Link } from "react-router-dom";
    ARROW LINK
    ═══════════════════════════════════════════════════════════════ */
 
-export default function ArrowLink({ to, label, color, size = "h-9 w-9" }) {
+type ArrowLinkProps = {
+  to: string;
+  label: string;
+  color: string;
+  /** Tailwind size classes for the circle. */
+  size?: string;
+};
+
+export default function ArrowLink({ to, label, color, size = "h-9 w-9" }: ArrowLinkProps) {
   return (
     <Link
       to={to}