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/go/include/wickra.h

@@ -128,6 +128,8 @@ typedef struct CalmarRatio CalmarRatio;
 
 typedef struct Camarilla Camarilla;
 
+typedef struct CandleReader CandleReader;
+
 typedef struct CandleVolume CandleVolume;
 
 typedef struct Cci Cci;
@@ -13736,6 +13738,16 @@ bool wickra_resampler_flush(struct Resampler *handle, struct WickraCandle *out);
 
 void wickra_resampler_free(struct Resampler *handle);
 
+struct CandleReader *wickra_candle_reader_new(const uint8_t *data, uintptr_t len);
+
+uintptr_t wickra_candle_reader_count(const struct CandleReader *handle);
+
+uintptr_t wickra_candle_reader_read(struct CandleReader *handle,
+                                    struct WickraCandle *out,
+                                    uintptr_t cap);
+
+void wickra_candle_reader_free(struct CandleReader *handle);
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif  // __cplusplus