feat(core): RDP client on IronRDP

clients::rdp connects over any caller-dialled TCP stream (direct, proxy
or SSH tunnel), upgrades to TLS and logs on with NLA (CredSSP/NTLM),
optionally falling back to TLS-only logon for servers without NLA such
as xrdp (credentials are passed so they log straight in). The server
certificate is pinned through a caller check on its SHA256 fingerprint
before any credentials are sent. The desktop decodes into the VNC
client's RGBA framebuffer; input (IronRDP's scancode/Unicode/mouse
operations), Display Control resizes and the deactivation-reactivation
sequence run on the session thread.

IronRDP's releases need three vendored patches (vendor/README.md):
picky and sspi with their RustCrypto release-candidate pins relaxed so
they share russh's stable versions (their own suites, 402 tests, pass
against them), and ironrdp-session with two unreleased upstream bitmap
fixes (#1486 stride, #1524 RDP6 orientation) without which xrdp desktops
render sheared.

Verified live against xrdp (scottyhardy/docker-remote-desktop): logon,
full desktop rendering, keyboard and mouse input.

rust/Cargo.toml

@@ -15,3 +15,9 @@ opt-level = 2
 
 [profile.release]
 lto = "thin"
+
+# IronRDP compatibility patches; see vendor/README.md for what each changes and when to drop it.
+[patch.crates-io]
+picky = { path = "vendor/picky" }
+sspi = { path = "vendor/sspi" }
+ironrdp-session = { path = "vendor/ironrdp-session" }