chore(release): bump version to 0.2.16

[wgqqqqq]

Summary

• bump product manifests from 0.2.15 to 0.2.16
• synchronize frontend, installer, relay, and Rust workspace versions
• refresh npm and Cargo lockfile package versions

Verification

• cargo check -p bitfun-relay-server
• cargo check --manifest-path BitFun-Installer/src-tauri/Cargo.toml
• product JSON version consistency check
• git diff --check

Notes

• pnpm run check:repo-hygiene was blocked locally by an unrelated untracked generate_intro_doc.cjs file containing a local absolute path; that file is not part of this PR.