feat: add setup did command to publish labeler identity

`cargo run --bin setup -- did` adds #atproto_label and #atproto_labeler to the
DID document via the PDS-signed PLC flow, prompting for the main password and
the emailed code. Splits setup into declare/did modules.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Cargo.toml

@@ -14,6 +14,8 @@ jacquard = { version = "=0.12.2", default-features = false, features = ["api_blu
 jacquard-axum = "=0.12.2"
 k256 = { version = "0.13", features = ["ecdsa"] }
 rand_core = { version = "0.6", features = ["getrandom"] }
+reqwest = { version = "0.12", default-features = false, features = ["rustls-tls", "json"] }
+rpassword = "7"
 rusqlite = { version = "0.37", features = ["bundled"] }
 serde = { version = "1", features = ["derive"] }
 serde_ipld_dagcbor = "0.6"