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.

Cargo.toml

@@ -14,7 +14,7 @@ members = [
 exclude = ["fuzz"]
 
 [workspace.package]
-version = "0.8.3"
+version = "0.8.4"
 authors = ["kingchenc <support@wickra.org>"]
 edition = "2021"
 rust-version = "1.86"
@@ -26,7 +26,7 @@ keywords = ["finance", "trading", "indicators", "technical-analysis", "ta"]
 categories = ["finance", "mathematics", "science"]
 
 [workspace.dependencies]
-wickra-core = { path = "crates/wickra-core", version = "0.8.3" }
+wickra-core = { path = "crates/wickra-core", version = "0.8.4" }
 
 thiserror = "2"
 rayon = "1.10"