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/index.d.ts

@@ -5973,3 +5973,14 @@ export declare class Resampler {
   /** Emit the final, still-open candle (or `null` if none is pending). */
   flush(): CandleValue | null
 }
+export type CandleReaderNode = CandleReader
+/**
+ * Parse OHLCV candles from a CSV string (header `timestamp,open,high,low,close,
+ * volume`; a leading UTF-8 BOM is stripped).
+ */
+export declare class CandleReader {
+  /** Parse the whole CSV up front; throws on a malformed header or row. */
+  constructor(csv: string)
+  /** Return every parsed candle as `{ open, high, low, close, volume, timestamp }`. */
+  read(): Array<CandleValue>
+}