refactor(tools): bin/{subject}/{method} layout; Go serve+watch modules

Move serve/ (module) -> bin/server, tools/ -> bin/tools, replace bin/kb-watch
bash with bin/watch Go package; self-executing Go shebangs bin/serve.go and
bin/kb/watch.go; Docker + CI + git/import + docs repointed. Multi-stage image
builds static serve+watch binaries (no Go runtime in container).

bin/tools/web-search/fixtures/throttled.json

@@ -0,0 +1 @@
+{"query": "Pflegegrad Test 4", "results": [], "answers": [], "corrections": [], "infoboxes": [], "suggestions": [], "unresponsive_engines": [["brave", "Suspended: too many requests"], ["duckduckgo", "CAPTCHA"], ["startpage", "Suspended: CAPTCHA"]]}