Migrate shared dependencies to workspace dependencies

[ljahier]

Summary

• Centralize version management by adding a [workspace.dependencies] section to the root Cargo.toml
• Migrate 20 shared dependencies (async-trait, tokio, tracing, serde, hyper, etc.) used by 2+ crates to workspace references
• Update doc examples in src/storage/mod.rs to reflect the new workspace syntax

Motivation

Dependency versions were duplicated across all 6 crates. Updating a shared dependency required editing multiple Cargo.toml files. With workspace dependencies, versions are defined once at the root and member
crates reference them with workspace = true, adding crate-specific features as needed.

Also updated doc examples to use the new syntax, ensuring consistency and reducing maintenance overhead.

Checking

• make pr-prep passes (fmt, build, clippy, tests, docs).

[hannesdejager]

Thank you very much @ljahier !