feat: JWT token generation API + auto-inject TORI_JWT in executor

- POST /tori/api/token — sign ES256 JWT with configurable private key
- exec.rs auto-generates and injects TORI_JWT env var for all commands
- Config: jwt_private_key field for PEM file path

Cargo.toml

@@ -28,3 +28,4 @@ mime_guess = "2"
 tokio-util = { version = "0.7", features = ["io"] }
 nix = { version = "0.29", features = ["signal"] }
 pulldown-cmark = "0.12"
+jsonwebtoken = "9"