Replace Fomantic search module with first-party autocomplete

Drops the 1565-line vendored Fomantic UI search jQuery plugin in favor
of a small first-party TypeScript module covering the three call sites
(repo, user, and team autocomplete). Adds an e2e regression suite that
exercises each search box.

Also fixes input/button vertical alignment in the four forms that wrap
a search box: the fomantic-era `tw-align-middle` workaround is replaced
by `flex-text-block` on the form, which is the codebase's standard
flex helper for this layout.

Co-Authored-By: Claude (Opus 4.7) <noreply@anthropic.com>

web_src/css/modules/search.css

@@ -1,4 +1,4 @@
-/* These are the remnants of the fomantic search module */
+/* Styles for the first-party search-box autocomplete (web_src/js/modules/fomantic/search.ts) */
 
 .ui.search {
   position: relative;