fix: forge URL derivation for bare IP hosts, add Cargo registry config

forge_url() now checks active context domain first before falling back
to production_host. Bare IP addresses are skipped in the host heuristic.
Adds .cargo/config.toml for the sunbeam Gitea Cargo registry.

sunbeam-sdk/Cargo.toml

@@ -3,6 +3,9 @@ name = "sunbeam-sdk"
 version = "0.1.0"
 edition = "2024"
 description = "Sunbeam SDK — reusable library for cluster management"
+repository = "https://src.sunbeam.pt/studio/cli"
+license = "MIT"
+publish = ["sunbeam"]
 
 [features]
 default = []