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).

examples/node/package-lock.json

@@ -17,7 +17,7 @@
     },
     "../../bindings/node": {
       "name": "wickra",
-      "version": "0.3.1",
+      "version": "0.4.0",
       "license": "PolyForm-Noncommercial-1.0.0",
       "devDependencies": {
         "@napi-rs/cli": "^2.18.0"
@@ -26,12 +26,12 @@
         "node": ">= 18"
       },
       "optionalDependencies": {
-        "wickra-darwin-arm64": "0.3.1",
-        "wickra-darwin-x64": "0.3.1",
-        "wickra-linux-arm64-gnu": "0.3.1",
-        "wickra-linux-x64-gnu": "0.3.1",
-        "wickra-win32-arm64-msvc": "0.3.1",
-        "wickra-win32-x64-msvc": "0.3.1"
+        "wickra-darwin-arm64": "0.4.0",
+        "wickra-darwin-x64": "0.4.0",
+        "wickra-linux-arm64-gnu": "0.4.0",
+        "wickra-linux-x64-gnu": "0.4.0",
+        "wickra-win32-arm64-msvc": "0.4.0",
+        "wickra-win32-x64-msvc": "0.4.0"
       }
     },
     "node_modules/wickra": {