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.

bindings/java/README.md

@@ -30,14 +30,14 @@ Maven:
 <dependency>
   <groupId>org.wickra</groupId>
   <artifactId>wickra</artifactId>
-  <version>0.8.3</version>
+  <version>0.8.4</version>
 </dependency>
 ```
 
 Gradle:
 
 ```kotlin
-implementation("org.wickra:wickra:0.8.3")
+implementation("org.wickra:wickra:0.8.4")
 ```
 
 The native library ships prebuilt per platform (Linux, macOS, Windows — x64 and

bindings/java/pom.xml

@@ -6,7 +6,7 @@
 
   <groupId>org.wickra</groupId>
   <artifactId>wickra</artifactId>
-  <version>0.8.3</version>
+  <version>0.8.4</version>
   <packaging>jar</packaging>
 
   <name>Wickra</name>