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.

docker/.dockerignore

@@ -0,0 +1,39 @@
+# Ignore Git directory
+.git
+.gitignore
+
+# Ignore Node.js modules (they will be installed in the Docker image)
+node_modules
+**/node_modules
+
+# Ignore build output (it will be generated in the Docker image)
+build
+dist
+
+# Ignore Docker files themselves (Caddyfile MUST stay in context for frontend build)
+Dockerfile
+Dockerfile.ws
+.dockerignore
+docker-compose.yml
+
+# Ignore any local environment files if you have them
+.env
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+# Ignore IDE and OS-specific files
+.vscode/
+.idea
+*.suo
+*.user
+*.userosscache
+*.sln.docstates
+Thumbs.db
+.DS_Store
+
+# Ignore local sqlite data + scratch diagnostics (never bake into image)
+data/
+scratch/
+tmp/