Continue the per-language `examples/<lang>/` restructure: move the three
Node example files (streaming.js, backtest.js, live_trading.js) out of
bindings/node/examples/ and into a top-level examples/node/ directory.
* `examples/node/package.json` is a `private` package that pulls the
native binding via `file:../../bindings/node` and lists `ws` as a
dev-dependency for the live-trading example. `require('..')` in each
file becomes `require('wickra')` — exactly what a downstream user would
write — and the file-header run instructions are updated to the new
two-step workflow (`npm install` in bindings/node, then in
examples/node).
* `backtest.js`'s default-CSV path becomes the much shorter
`__dirname/../data/btcusdt-1d.csv` from the new location.
* `bindings/node/package.json` drops the now-unused `ws` devDependency.
* `.gitignore` is broadened from `bindings/node/node_modules/` to
`**/node_modules/` so the new `examples/node/node_modules/` directory is
not tracked.
* The README "Languages" table, project-layout block and
`examples/README.md` Node section are updated for the new paths and run
commands.
Verified by running `node backtest.js` (3200 BTCUSDT daily bars, matching
output), `node streaming.js`, and `node --check live_trading.js` from the
new location.
kingchenc