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.lock

@@ -1944,7 +1944,7 @@ dependencies = [
 
 [[package]]
 name = "wickra"
-version = "0.8.3"
+version = "0.8.4"
 dependencies = [
  "approx",
  "criterion",
@@ -1955,7 +1955,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-bench"
-version = "0.8.3"
+version = "0.8.4"
 dependencies = [
  "criterion",
  "kand",
@@ -1967,14 +1967,14 @@ dependencies = [
 
 [[package]]
 name = "wickra-c"
-version = "0.8.3"
+version = "0.8.4"
 dependencies = [
  "wickra-core",
 ]
 
 [[package]]
 name = "wickra-core"
-version = "0.8.3"
+version = "0.8.4"
 dependencies = [
  "approx",
  "proptest",
@@ -1984,7 +1984,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-data"
-version = "0.8.3"
+version = "0.8.4"
 dependencies = [
  "approx",
  "csv",
@@ -2001,7 +2001,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-examples"
-version = "0.8.3"
+version = "0.8.4"
 dependencies = [
  "serde_json",
  "tokio",
@@ -2011,7 +2011,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-node"
-version = "0.8.3"
+version = "0.8.4"
 dependencies = [
  "napi",
  "napi-build",
@@ -2021,7 +2021,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-python"
-version = "0.8.3"
+version = "0.8.4"
 dependencies = [
  "numpy",
  "pyo3",
@@ -2030,7 +2030,7 @@ dependencies = [
 
 [[package]]
 name = "wickra-wasm"
-version = "0.8.3"
+version = "0.8.4"
 dependencies = [
  "console_error_panic_hook",
  "js-sys",