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/data/bannerConfig.d.ts

@@ -0,0 +1,10 @@
+/* Types for bannerConfig.js. */
+
+export type BannerPart = { text: string; href?: string; external?: boolean };
+
+export declare const SITE_BANNER: {
+  enabled: boolean;
+  id: string;
+  content: BannerPart[];
+  dismissible: boolean;
+};