feat(saml): wire SAML 2.0 SSO end-to-end (pure-Rust) + Settings/Storage UI consolidation (v0.5.1)

SAML SSO (the config was storage-only since v0.4.5; now it logs you in):
- New openpxe-core::saml — pure-Rust SP built on bergshamra (XML-DSig +
  exclusive c14n via RustCrypto, no OpenSSL/xmlsec/libxml2). The static
  musl binary stays C-free; samael was rejected for hard-requiring OpenSSL.
  * metadata.rs   — parse IdP EntityDescriptor (SSO URLs + signing certs),
                    build our SP metadata.
  * authn_request.rs — build + HTTP-Redirect-encode AuthnRequests.
  * response.rs   — verify the signature against the pinned IdP cert
                    (trusted_keys_only + strict_verification for XSW),
                    then enforce Status/Destination/Audience/time-bounds/
                    signature-scope. Stateless; returns the IDs the HTTP
                    layer needs.
- http-api saml_routes: GET /api/sso/login (302 to IdP), POST /api/sso/acs
  (verify -> InResponseTo correlation / IdP-initiated gating / assertion
  replay guard -> mint operator session -> 302), GET /api/sso/metadata.
  Added to the pre-auth allowlist; /api/sso config stays gated.
- SsoConfig gains entity_id (SP Entity ID, defaults to public base URL)
  and allow_idp_initiated (default off), mirroring FleetDM.
- Access model: any IdP-authenticated, cryptographically-verified user gets
  an operator session (single-tier; local admin remains the fallback owner).
- Login page: the "Sign in with <IdP>" button now drives the real flow and
  surfaces sso_error redirects.

UI consolidation:
- Removed the Advanced sidebar tab; folded its webhook-notifications +
  API-reference cards into a collapsible "Advanced" disclosure at the
  bottom of Settings.
- Merged the Storage tab's separate SMB and NFS cards into one "Remote
  shares" card with a protocol dropdown and a unified, protocol-badged
  table. No backend changes — same /api/smb-shares + /api/nfs-shares.

Tests: 17 SAML core tests (accept + reject tampered/unsigned/wrong-key/
wrong-audience/expired/future/wrong-issuer/non-success) and 6 ACS
integration tests (happy path, IdP-initiated gating, SP correlation,
replay, garbage). Full workspace: 206 tests green, clippy clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

Cargo.toml

@@ -12,7 +12,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.5.0"
+version = "0.5.1"
 edition = "2021"
 rust-version = "1.95"
 license = "MIT OR Apache-2.0"
@@ -71,6 +71,20 @@ nfs3_types = "0.5"
 # to match reqwest and stay musl-static-friendly — no OpenSSL.
 lettre = { version = "0.11", default-features = false, features = ["smtp-transport", "tokio1-rustls-tls", "builder", "hostname"] }
 
+# v0.5.1: pure-Rust SAML 2.0 Service Provider. bergshamra does XML-DSig
+# verification + exclusive c14n with RustCrypto (no OpenSSL/xmlsec/libxml2
+# C deps), so the static musl binary stays OpenSSL-free — samael was
+# rejected precisely because it hard-requires OpenSSL. We build the thin
+# SP layer (AuthnRequest, metadata parse, SAMLResponse semantics) on top.
+bergshamra = "0.4"
+roxmltree = "0.21"
+quick-xml = "0.40"
+x509-parser = "0.18"
+# flate2 default backend is miniz_oxide (pure Rust) — do NOT enable the
+# zlib/zlib-ng C backends, which would break the musl-static build.
+flate2 = "1.1"
+base64 = "0.22"
+
 openpxe-core = { path = "crates/core" }
 openpxe-dhcp-proxy = { path = "crates/dhcp-proxy" }
 openpxe-tftp = { path = "crates/tftp" }