Let go of the keyboard when a name is finished

Pressing Enter on a person's name committed it and then kept the field
focused, so on a tablet the on-screen keyboard stayed up over the faces
the user had pressed Enter to get back to. The name looked accepted and
the screen looked stuck.

`Field` grows `release-focus()`, the other half of the `take-focus()` it
already had, and the Identity screen calls it from `accepted`. A function
rather than a property for the reason the existing one gives: focus is an
event, and bound to a property it would fight anything else that took it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ui/dr-ui/ui/widgets.slint

@@ -633,6 +633,19 @@ export component Field inherits Rectangle {
         input.select-all();
     }
 
+    /// Give the keyboard back.
+    ///
+    /// The other half of `take-focus`, and the one a field that *submits*
+    /// needs: pressing Enter on a name has finished with the name, but Slint
+    /// leaves the entry focused, so on a tablet the on-screen keyboard stays
+    /// up covering the very thing the user just named. Nothing else on those
+    /// screens takes focus on its own, so the field has to let go itself.
+    ///
+    /// A function and not a property, for the reason `take-focus` gives.
+    public function release-focus() {
+        input.clear-focus();
+    }
+
     height: Theme.touch-target;
     border-radius: Theme.radius;
     border-width: 1px;