📚 Improve Aptos Rust SDK Documentation & Keyless Support

## 📝 Issue Summary
The latest [Aptos Rust SDK] docs on docs.rs fail to build, leaving no API reference or examples—particularly for **keyless** account creation. Our team is building a Telegram bot in Rust using [Teloxide] and relies on keyless flows to generate user accounts without managing private keys.

## 🔍 Steps to Reproduce
1. Go to https://docs.rs/crate/aptos-sdk/latest/builds
2. Observe the “build failed” indicator and missing content
3. Search the sidebar for “keyless” or `AccountClient`—nothing appears

## ✅ Expected Behavior
- **Error-free documentation** for the `aptos-sdk` crate on docs.rs
- **Keyless API reference**, e.g.
```rust
let keyless_client = AccountClient::new_keyless(base_url, auth_token)?;
let account = keyless_client.create().await?;
```
- **Code snippets** demonstrating:
- Initializing a keyless client
- Creating a keyless account
- Signing and submitting transactions
- Querying account state
- **Examples** in both high-level and low-level modules, plus integration tests or a playground link

## ❌ Actual Behavior
- docs.rs reports build failures; no pages are rendered
- No documentation for keyless account flows
- Developers cannot integrate Aptos keyless wallets in Rust projects

## 🖥️ Environment
- **aptos-sdk** version: latest on crates.io
- **Rust toolchain**: stable-x86_64-unknown-linux-gnu
- **OS**: Manjaro Linux (kernel 6.x)
- **Docs host**: docs.rs

[Teloxide]: https://github.com/teloxide/teloxide
[Aptos Rust SDK]: https://docs.rs/aptos-sdk/latest

Reproduce the latest aptos-sdk documentation build failure on docs.rs first; the issue names no repository files, tests, or entry points to inspect. Trace the documented AccountClient keyless flow, including initialization, account creation, signing, transaction submission, and state queries, and consider the work done when docs.rs renders successfully with those examples and API references.

Written by the indexing model from the issue text.