fix(docker): single container (caddy+node), ESM adapters fix blank page

Docker: moved all docker files to docker/ tree (was conflated with
upstream Dockerfile at root + server/Dockerfile). Single container now:
caddy (front, serves static + proxies /api /ws) + node backend (internal
:4001). Node never exposed. entrypoint.sh runs both. Compose: one service.

Blank page root cause: storage adapters had inconsistent module systems.
firebase.js = ESM (export). ws.js + memory.js = CJS (module.exports).
CRA prod build = ESM strict -> CJS runtime crash, blank root. Dev mode
lenient, masked bug. First ws prod build (docker) = first exposure.
Never dev/prod split intended; just inconsistency from M2 era.

Fix: all adapters ESM. ws.js lazy-loads 'ws' pkg via dynamic import()
(Node/jest only; browser uses global WebSocket). index.js static
imports. server jest: added babel.config.js (preset-env, node target)
to transform ESM for jest.

Test: src/tests/StorageEsm.test.js — 4 tests grep all adapters for
module.exports / require(). Regression guard catches CJS leak.

Verified: docker page renders (root 4534 chars, UI visible).
server 24 green, shared 90 green, FE ESM 4 green.

src/storage/ws.js

@@ -5,11 +5,10 @@
 'use strict';
 
 // Native browser WebSocket if present, else ws pkg (Node/jest).
+// Lazy load ws pkg so CRA prod build (ESM) doesn't choke on require().
 let WebSocketImpl;
 if (typeof WebSocket !== 'undefined') {
   WebSocketImpl = WebSocket;
-} else {
-  WebSocketImpl = require('ws').WebSocket;
 }
 
 function createWsStorage({ baseUrl, wsUrl } = {}) {
@@ -47,7 +46,15 @@ function createWsStorage({ baseUrl, wsUrl } = {}) {
   function ensureWs() {
     if (wsReady) return wsReady;
     wsReady = new Promise((resolve, reject) => {
-      ws = new WebSocketImpl(WS);
+      (async () => {
+        // Node/jest only: load ws pkg via dynamic import. Browser uses global
+        // WebSocket. Avoids require() in CRA prod ESM bundle (webpack crash).
+        let WsClass = WebSocketImpl;
+        if (!WsClass) {
+          const wsPkg = await import('ws');
+          WsClass = wsPkg.WebSocket;
+        }
+        ws = new WsClass(WS);
       const onOpen = () => {
         const isReconnect = everConnected;
         everConnected = true;
@@ -99,6 +106,7 @@ function createWsStorage({ baseUrl, wsUrl } = {}) {
         ws.addEventListener('close', onClose);
         ws.addEventListener('message', onMessage);
       }
+      })();
     });
     return wsReady;
   }
@@ -226,4 +234,4 @@ function createWsStorage({ baseUrl, wsUrl } = {}) {
   return storage;
 }
 
-module.exports = { createWsStorage };
+export { createWsStorage };