release: bump 0.8.3 -> 0.8.4 (#256)

Version bump `0.8.3` → `0.8.4`.

Ships the work merged via #254:

### Fixed
- A single non-finite (NaN/inf) tick no longer poisons indicator state — 38 more scalar/pairwise indicators (linear-regression family, rolling quantiles/IQR, `Variance`/`StdDev`-derived stats, `Kurtosis`/`Skewness`, trailing stops, `KalmanHedgeRatio`, `SpreadBollingerBands`, …) now reject non-finite input and return `None`, joining the 16 pairwise indicators fixed earlier.

### Added
- Catalogue-wide property-based invariant harness (`crates/wickra-core/tests/invariants.rs`) asserting `batch == streaming`, `reset == fresh`, and non-finite-input rejection for every indicator and bar-builder.

### Changed
- CI: every job now has a runtime cap and the flaky Node test step auto-retries.
- Documentation accuracy fixes in `SECURITY.md`, `ARCHITECTURE.md`, and `THREAT_MODEL.md`.

Bump touches the manual release touchpoints only (`Cargo.toml`/`Cargo.lock`, Python/Node/Java/C#/R manifests, lockfiles, `SECURITY.md`, `CHANGELOG.md`). docs/webpage version strings are left to `sync-about.yml` on the tag.

examples/node/package-lock.json

@@ -17,7 +17,7 @@
     },
     "../../bindings/node": {
       "name": "wickra",
-      "version": "0.8.3",
+      "version": "0.8.4",
       "license": "MIT OR Apache-2.0",
       "devDependencies": {
         "@napi-rs/cli": "^2.18.0"
@@ -26,12 +26,12 @@
         "node": ">= 18"
       },
       "optionalDependencies": {
-        "wickra-darwin-arm64": "0.8.3",
-        "wickra-darwin-x64": "0.8.3",
-        "wickra-linux-arm64-gnu": "0.8.3",
-        "wickra-linux-x64-gnu": "0.8.3",
-        "wickra-win32-arm64-msvc": "0.8.3",
-        "wickra-win32-x64-msvc": "0.8.3"
+        "wickra-darwin-arm64": "0.8.4",
+        "wickra-darwin-x64": "0.8.4",
+        "wickra-linux-arm64-gnu": "0.8.4",
+        "wickra-linux-x64-gnu": "0.8.4",
+        "wickra-win32-arm64-msvc": "0.8.4",
+        "wickra-win32-x64-msvc": "0.8.4"
       }
     },
     "node_modules/wickra": {