Convert src/ JavaScript modules to TypeScript

Renames every .js module under src/ to .ts (api, useResource,
adminSchema, navConfig, adminNav and src/data/*) and points imports,
comments and the seed script's module paths at the new names. Their
types now come from inference; no .d.ts files and no shape
interfaces.

tsc stays strict (noImplicitAny off). The errors inference leaves
behind get the lightest fix that clears them: `any` on empty state,
contexts and list defaults, `: any` on components with optional or
spread props, class fields on ApiError, and option shapes on
get/useResource.

Kept as real types, since they belong to modules that were already
TypeScript and later features import them: PageShell's ShellSection
and props, useContent's corrected record types (website/email/
instagram are bare strings) and EventListItem, and TimelineRef's
orgKind.

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

src/lib/useHistory.ts

@@ -26,7 +26,7 @@
  */
 
 import { useCallback, useEffect, useState } from 'react'
-import { get, invalidate, ApiError } from './api.js'
+import { get, invalidate, ApiError } from './api.ts'
 import type { TimelineItem } from './timeline'
 
 const PATH = '/history'