Prepare Java SDK for JDK 25 (LTS), harden CI, and upgrade build tooling

[emmanuel-keller]

What's in this PR

This pull request ensures the SurrealDB Java driver is ready for the upcoming JDK 25 LTS release, strengthens CI security, and brings build dependencies up to date. No public API changes are introduced — this is a maintenance and compatibility update.

Changes

• JDK 25 compatibility — Added JDK 25 to the CI test matrix and set options.release = 8 to guarantee bytecode compatibility back to Java 8 while compiling on newer JDKs.
• CI security hardening — Pinned all GitHub Actions to commit SHAs instead of mutable tags, preventing supply-chain attacks via tag re-pointing.
• Gradle wrapper upgrade — Bumped Gradle wrapper from its previous version to 8.14.4.
• Cargo dependency alignment — Updated Rust-side Cargo.toml dependencies to match the versions used by SurrealDB core, reducing version drift.
• Rust code formatting — Minor formatting and readability improvements in the native Rust bridge code (no behavioral changes).

Impact for Java driver users

• No breaking changes. The driver remains compatible with Java 8+.
• Improved confidence in forward-compatibility with JDK 25 LTS.
• Stronger CI pipeline integrity protects the supply chain of published artifacts.