feedback5 R1: pure move — the top-level code of server/index.js goes to server/http/ (config, common, files, static, media, buildTag, websocket, boot) verbatim; index.js imports it and re-exports the same 15 names, startServer and main are untouched

Only changes besides the move: `export` on helpers another module now needs (sendError, sendJson, splitUrl, GzipCache,
isNotModified, serveFile, serveMedia, noopLog, makeLogger), ROOT resolves two levels up from server/http/config.js
(same path), and short headers on the new files.

server/http/websocket.js

@@ -0,0 +1,4 @@
+// server/http/websocket.js — the WebSocket endpoint (moved from server/index.js).
+
+/** Inbound WebSocket frame limit (DESIGN §8). */
+export const WS_MAX_PAYLOAD = 64 * 1024;