release: bump 0.8.8 -> 0.8.9 (#285)

Maintenance release — supply-chain and CI housekeeping only. No library code or
public API changes.

### Security
- Triaged the pyo3 advisories RUSTSEC-2026-0176 / RUSTSEC-2026-0177 as not
  affecting Wickra (vulnerable APIs unreachable from the binding; fix blocked
  upstream by rust-numpy pinning pyo3 `^0.28`). Recorded in `deny.toml` and
  `osv-scanner.toml`.

### Changed
- Java binding: `central-publishing-maven-plugin` 0.5.0 → 0.10.0.
- CI GitHub Actions bumped to latest (checkout, setup-go, setup-java,
  codeql-action, taiki-e/install-action).
- Added a Maven ecosystem to Dependabot.

Version bumped across all manifests/lockfiles via `bump_version.py`; Cargo.lock
refreshed. CHANGELOG `[0.8.9]` filled. Tag/publish to follow on explicit GO.

bindings/r/DESCRIPTION

@@ -1,7 +1,7 @@
 Package: wickra
 Type: Package
 Title: Streaming-First Technical Indicators
-Version: 0.8.8
+Version: 0.8.9
 Authors@R: person("Wickra contributors", role = c("aut", "cre"), email = "support@wickra.org")
 Description: R bindings for the Wickra technical-analysis library over its C ABI
     hub. Exposes 514 indicators, each an O(1) streaming state machine shared with