release: bump 0.9.3 -> 0.9.4 (#326)

Packaging fix for the `0.9.3` data layer.

`0.9.3` published to crates.io, Maven Central, NuGet, npm, and the Go mirror, but
the **Linux Python wheels failed to build**, so `Publish to PyPI` was skipped and
no GitHub Release was attached. Root cause: the `live-binance` data layer links
`native-tls` -> `openssl-sys`, and the `manylinux` / `musllinux` wheel-build
containers do not ship the system OpenSSL headers. The native macOS and Windows
wheels were unaffected (system TLS), which is why CI — running Python natively on
the runners, where OpenSSL is present — stayed green.

### Changes
- **`ci`**: install the OpenSSL headers inside the wheel container via
  maturin-action's `before-script-linux` (`openssl-devel` on `manylinux`,
  `openssl-dev` on `musllinux`) before maturin compiles. No library code changed.
- **`release: bump 0.9.3 -> 0.9.4`**: version-string bump across the manual
  touchpoints + `CHANGELOG` `[0.9.4]`.

`0.9.4` is functionally identical to `0.9.3`; it exists only because the already-
published registries cannot re-release `0.9.3`. PyPI publishes for the first time
starting at `0.9.4` (it skips `0.9.3`).

Cargo.toml

@@ -14,7 +14,7 @@ members = [
 exclude = ["fuzz"]
 
 [workspace.package]
-version = "0.9.3"
+version = "0.9.4"
 authors = ["kingchenc <support@wickra.org>"]
 edition = "2021"
 rust-version = "1.86"
@@ -26,8 +26,8 @@ keywords = ["finance", "trading", "indicators", "technical-analysis", "ta"]
 categories = ["finance", "mathematics", "science"]
 
 [workspace.dependencies]
-wickra-core = { path = "crates/wickra-core", version = "0.9.3" }
-wickra-data = { path = "crates/wickra-data", version = "0.9.3" }
+wickra-core = { path = "crates/wickra-core", version = "0.9.4" }
+wickra-data = { path = "crates/wickra-data", version = "0.9.4" }
 
 thiserror = "2"
 rayon = "1.10"