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.lock

@@ -1775,7 +1775,7 @@ dependencies = [
 
 [[package]]
 name = "wickra"
-version = "0.9.3"
+version = "0.9.4"
 dependencies = [
  "approx",
  "criterion",
@@ -1786,7 +1786,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-bench"
-version = "0.9.3"
+version = "0.9.4"
 dependencies = [
  "criterion",
  "kand",
@@ -1798,7 +1798,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-c"
-version = "0.9.3"
+version = "0.9.4"
 dependencies = [
  "tokio",
  "wickra-core",
@@ -1807,7 +1807,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-core"
-version = "0.9.3"
+version = "0.9.4"
 dependencies = [
  "approx",
  "proptest",
@@ -1817,7 +1817,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-data"
-version = "0.9.3"
+version = "0.9.4"
 dependencies = [
  "approx",
  "csv",
@@ -1836,7 +1836,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-examples"
-version = "0.9.3"
+version = "0.9.4"
 dependencies = [
  "serde_json",
  "tokio",
@@ -1846,7 +1846,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-node"
-version = "0.9.3"
+version = "0.9.4"
 dependencies = [
  "napi",
  "napi-build",
@@ -1858,7 +1858,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-python"
-version = "0.9.3"
+version = "0.9.4"
 dependencies = [
  "bytemuck",
  "pyo3",
@@ -1869,7 +1869,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-wasm"
-version = "0.9.3"
+version = "0.9.4"
 dependencies = [
  "console_error_panic_hook",
  "js-sys",