fix(cli): add missing auth subcommand

[fchange]

Summary

Fixes #761.

Adds the missing openfang auth CLI group referenced by the [auth] config docs so users can generate password_hash values from the terminal.

Changes

• add openfang auth hash-password [password] to generate SHA256 hashes for [auth].password_hash
• add openfang auth status [--json] to report whether dashboard auth is configured
• add CLI parsing and hash regression tests for the new subcommands
• keep the existing config comment accurate without changing config semantics

Testing

• cargo clippy --workspace --all-targets -- -D warnings passes
• cargo test --workspace passes
• Live integration tested (if applicable)
  • CLI smoke: cargo run -p openfang-cli -- auth hash-password secret123
  • CLI smoke: OPENFANG_HOME=$(mktemp -d) cargo run -p openfang-cli -- auth status --json

Security

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