release: bump 0.3.1 -> 0.4.0 (#89)

Minor release. The headline user-facing change is the Node binding now
rejecting invalid indicator periods instead of silently clamping period 0
to 1 (matches Python/WASM/core); plus per-ecosystem binding READMEs and a
corrected MSRV statement in CONTRIBUTING. See CHANGELOG [0.4.0].

- Cargo.toml (workspace.package + wickra-core dep) + Cargo.lock (6 members)
- bindings/python/pyproject.toml
- bindings/node/package.json (version + 6 optionalDependencies) + package-lock.json
- bindings/node/npm/*/package.json (6 platform subpackages)
- examples/node/package-lock.json (wickra-* platform pins)
- CHANGELOG: [Unreleased] -> [0.4.0] - 2026-05-31 + compare URL

No tag pushed (release publish is a separate, user-confirmed step).

Cargo.lock

@@ -1867,7 +1867,7 @@ dependencies = [
 
 [[package]]
 name = "wickra"
-version = "0.3.1"
+version = "0.4.0"
 dependencies = [
  "approx",
  "criterion",
@@ -1878,7 +1878,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-core"
-version = "0.3.1"
+version = "0.4.0"
 dependencies = [
  "approx",
  "proptest",
@@ -1888,7 +1888,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-data"
-version = "0.3.1"
+version = "0.4.0"
 dependencies = [
  "approx",
  "csv",
@@ -1915,7 +1915,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-node"
-version = "0.3.1"
+version = "0.4.0"
 dependencies = [
  "napi",
  "napi-build",
@@ -1925,7 +1925,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-python"
-version = "0.3.1"
+version = "0.4.0"
 dependencies = [
  "numpy",
  "pyo3",
@@ -1934,7 +1934,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-wasm"
-version = "0.3.1"
+version = "0.4.0"
 dependencies = [
  "console_error_panic_hook",
  "js-sys",