fix: select crypto provider (#903)

[hello-world-bfree]

Summary

Install the rustls CryptoProvider (ring) at kernel boot to fix a panic when channel adapters (e.g. Discord) open TLS connections. Rustls 0.23+ can't auto-select a provider when both ring and aws-lc-rs are in the dependency tree. Resolves #903

Note

There's also an issue with the Discord Gateway protocol. At the moment the client does not send a heartbeat. This adds that in.

Changes

• Added rustls (with ring feature) as a workspace dependency - Added rustls to openfang-kernel crate - Call install_default() as the first line of boot_with_config(), before any reqwest::Client construction

Testing

• cargo clippy --workspace --all-targets -- -D warnings passes
• cargo test --workspace passes
• Live integration tested (if applicable)

Security

• No new unsafe code
• No secrets or API keys in diff
• User input validated at boundaries

[jaberjaber23]

Reviewed. Two issues: (1) The Discord heartbeat fix is unrelated to the crypto provider fix. Split into two PRs. (2) The install_default() Result is silently discarded with let _ =. At minimum add a debug log.