Implement native InputCapture with private EIS receiver transport

Add consent, zones and outside-edge barriers, connection-scoped leases, bounded input queues and keyboard/pointer forwarding. Restore local input on release, locking, topology or keymap changes, receiver loss and emergency escape. Preserve held-key state and distinguish finger stops from absent scroll axes.

Validation: independent review cleared; 5 native InputCapture unit tests; 32 portal tests; official D-Bus contract checks on a private bus; real installed libei receiver interoperability test. Live physical barrier and consent interaction remain to be checked in a desktop session.

compositor/src/session_lock.rs

@@ -123,6 +123,7 @@ impl SessionLockHandler for Ferese {
         }
         self.cancel_logout_confirmation();
         self.session_lock.active = true;
+        self.input_capture.disable_all();
         self.portal_session.set_locked(true);
         self.session_lock.owner = Some(confirmation.ext_session_lock().clone());
         self.session_lock.confirmation = Some(confirmation);