feat(data): expose CandleReader (CSV) natively in all 10 languages (#311)

Add the data-layer CSV candle reader to every binding so loading OHLCV
candles from a CSV no longer needs a per-language CSV/dataframe dependency.

- C ABI: wickra_candle_reader_new(bytes, len) / _count / _read / _free over
  an opaque CandleReader handle (parse the whole buffer up front, then drain).
- Native: Node/WASM CandleReader.read() -> Candle[], Python read() -> list[tuple].
- C-ABI languages: Go Read() []Candle, C# Candle[] Read(), Java Candle[] read(),
  R read() S3 generic (n x 6 matrix); C / C++ call the C ABI directly.
- Cross-language golden testdata/golden/data_csv*.csv pins the parsed candles
  bit-for-bit across every binding.

Verified locally across Rust (test+clippy+fmt), Node, WASM, Python, C#, Go,
Java, R, and the C/C++ cmake parity suite.

bindings/node/__tests__/data_layer.test.js

@@ -8,7 +8,7 @@ const test = require('node:test');
 const assert = require('node:assert/strict');
 const fs = require('node:fs');
 const path = require('node:path');
-const { TickAggregator, Resampler } = require('..');
+const { TickAggregator, Resampler, CandleReader } = require('..');
 
 const GOLDEN = path.resolve(__dirname, '..', '..', '..', 'testdata', 'golden');
 
@@ -52,6 +52,13 @@ test('tick aggregator gap-fill matches the golden candles', () => {
   assertCandles(run(true), readCsv('data_candles_gap'), 'gap');
 });
 
+test('candle reader matches the golden candles', () => {
+  const csv = fs.readFileSync(path.join(GOLDEN, 'data_csv.csv'), 'utf8');
+  const reader = new CandleReader(csv);
+  const got = reader.read().map((c) => [c.open, c.high, c.low, c.close, c.volume, c.timestamp]);
+  assertCandles(got, readCsv('data_csv_candles'), 'candle-reader');
+});
+
 const INPUT = readCsv('input'); // open,high,low,close,volume (timestamp = row index)
 
 function runResample() {