feat: allow origin-scoped target headers from env (#65)

Enable authenticated scans across the HTTP arsenal while binding configured credentials to an exact target origin.

Includes case-insensitive per-request overrides, cross-origin redirect containment, protected curl configuration, result redaction, documentation, and regression coverage.

Co-authored-by: Fred Blaise <fred.blaise@protonmail.com>

.env.example

@@ -11,6 +11,16 @@ TOGETHER_API_KEY=
 HUGGINGFACE_TOKEN=
 REPLICATE_API_TOKEN=
 
+# ── Target authentication (both values are required) ──
+# Exact origin that may receive the configured headers (scheme + host + optional port).
+# TEMPEST_TARGET_ORIGIN=https://target.example
+# JSON object of headers injected into HTTP requests to that exact origin.
+# Explicit per-request headers override these defaults case-insensitively.
+# Bearer token:   TEMPEST_TARGET_HEADERS={"Authorization":"Bearer eyJhbGc..."}
+# Cookie:         TEMPEST_TARGET_HEADERS={"Cookie":"session=abc123"}
+# Multiple:       TEMPEST_TARGET_HEADERS={"Authorization":"Bearer token","X-Tenant":"acme"}
+# TEMPEST_TARGET_HEADERS=
+
 # ── GitHub (xbow-bench challenge fetch / gh operations) ──
 GITHUB_TOKEN=