Adds `BinanceRest::fetch_klines` to `wickra-data`: a blocking historical kline
downloader (`GET /api/v3/klines`) and the historical counterpart to the F4 live
`BinanceFeed`. It is the last native data-layer primitive needed to drop
third-party HTTP/JSON download helpers (`jackson`, `jsonlite`, `urllib`, …) from
the examples.
## What
- **Core** (`wickra-data`): `fetch_klines(symbol, interval, limit, start?, end?)`
built on `ureq` with native-tls — sharing the exact same TLS backend
(native-tls 0.2 / SChannel) as the existing tokio-tungstenite live feed, so the
two pull one TLS stack, not two. Parses Binance's 12-element array rows via the
existing serde infrastructure into validated `Candle`s. Blocking by design (a
one-shot request needs no async runtime; the FFI boundary is synchronous
anyway). Nine mock-HTTP-server tests cover parse / empty / limit / transport /
JSON / invariant-violation paths.
- **C ABI**: `wickra_binance_fetch_klines(...)` (blocking drain into a caller
buffer, `-1` on error) + regenerated cbindgen header and its vendored Go copy.
- **Bindings**: native Node `fetchBinanceKlines` / Python `fetch_binance_klines`;
generated Go `FetchBinanceKlines` / C# `BinanceFeed.FetchKlines` / Java
`BinanceFeed.fetchKlines` / R `fetch_binance_klines`. C / C++ call the C ABI
directly. **WASM is excluded** (browsers use the host `fetch`).
The four C-ABI bindings are regenerated from the ScriptHelpers generators (not
hand-edited); the regen diff is exactly the new wrapper in each.
## Verification
All ten toolchains green locally: Rust (`cargo test`/`clippy`/`fmt`), Node, Python,
Go, C#, Java, R (`R CMD INSTALL` + smoke), WASM (`cargo check`, confirmed `ureq`
is not pulled). Each binding has an error-path smoke test; the parse/HTTP success
path is covered by the Rust mock-server tests.
No release in this PR — ships with the data-layer + numpy bundle later.
kingchenc
2ae76bb90e