Make the home page's AS name search work (closes #151)

The AS Name Search card on the home page said the search was coming
soon. It now asks the new GET /api/v1/search/as?q=<text>, which
searches the AS list built into asinfo, and lists the matches as links
to their AS pages. An empty q answers 400. asinfo.Search now ignores
case and returns its matches in AS number order.

A match can be an AS that the database does not hold yet. Its AS page
and /api/v1/as/{asn} now answer with its handle and description from
asinfo and no prefixes, instead of 404. Empty prefix lists in that JSON
answer are [] rather than null.

Model: opus-5-5

TODO.md

@@ -33,6 +33,11 @@ tested.
 
 # Completed Steps
 
+- 2026-10-26: the home page's AS name search lists the ASes whose handle or
+  description holds the text, as links to their pages, from the new
+  `/api/v1/search/as`; the search ignores case. An AS page answers for an AS
+  that only the AS list built into RouteWatch knows, with no prefixes (closes
+  #151)
 - 2026-10-19: README "HTTP Endpoints" lists every route with what it answers,
   "Database Schema" matches `schema.sql`, and the rest of the README matches the
   code; this file brought up to date (closes #72)