feat(ostool): unify TLS provider via shared HTTP client builder

Introduce a centralized http_client module that installs the Ring crypto
provider before constructing any reqwest client, ensuring rustls is
consistently configured across auth, board, and build pipelines. Switch
reqwest and ureq dependencies to rustls-based TLS without the aws-lc-rs
provider, and add the workspace rustls dependency to ostool. Update
docs/api.md to cover the Management API surface.

Author: ZCShou

Cargo.lock

@@ -36,3 +36,4 @@ schemars = {version = "1.0.4", features = ["derive"]}
 env_logger = "0.11"
 
 tokio = {version = "1", features = ["full"]}
+rustls = {version = "0.23", default-features = false, features = ["ring"]}