feat: unify RLN types, refactor public APIs, add full (de)serialization, align FFI/WASM/APIs, simplify errors, update docs/examples, and clean up zerokit (#355)

# Changes

- Unified the `RLN` struct and core protocol types across public, FFI,
and WASM so everything works consistently.
- Fully refactored `protocol.rs` and `public.rs` to clean up the API
surface and make the flow easier to work with.
- Added (de)serialization for `RLN_Proof` and `RLN_ProofValues`, and
matched all C, Nim, WASM, and Node.js examples.
- Aligned FFI and WASM behavior, added missing APIs, and standardized
how witness are created and passed around.
- Reworked the error types, added clearer verification messages, and
simplified the overall error structure.
- Updated variable names, README, Rust docs, and examples across the
repo, updated outdated RLN RFC link.
- Refactored `rln-cli` to use the new public API, removed
serialize-based cli example, and dropped the `eyre` crate.
- Bumped dependencies, fixed CI, fixed `+atomic` flags for latest
nightly Rust and added `Clippy.toml` for better fmt.
- Added a `prelude.rs` file for easier use, cleaned up public access for
types and types import across zerokit modules.
- Separated keygen, proof handling, slashing logic, and witness into
protocol folder.

Cargo.toml

@@ -4,7 +4,7 @@ exclude = ["rln-cli", "rln-wasm"]
 resolver = "2"
 
 # Compilation profile for any non-workspace member.
-# Dependencies are optimized, even in a dev build. This improves dev performance
-# while having neglible impact on incremental build times.
+# Dependencies are optimized, even in a dev build.
+# This improves dev performance while having negligible impact on incremental build times.
 [profile.dev.package."*"]
 opt-level = 3