feat: enable tauri auto-updater configuration - #10

Summary

• enable Tauri updater artifact generation (createUpdaterArtifacts: true)
• configure updater endpoint and generated minisign public key
• bump app version to 0.3.1 across JS, Rust, and Tauri config
• align release workflow asset prefix with product name (Dictx)

Validation

• bun run lint
• bun run build
• cargo test

Notes

• cargo clippy -- -D warnings currently fails due existing repository-wide lint debt unrelated to this PR.