add all crates: domain, protocol, application, client, adapters, ESP32 firmware

Server: domain (entities, value objects, ports), protocol (postcard wire types),
application (config service, data projection), adapters (config-memory, tcp-server),
bootstrap (composition root with fake data).

Client: client-domain (layout engine, render tree, HAL ports),
client-application (message handling, repaint commands),
adapters (tcp-client, display-terminal), client-desktop (end-to-end working).

ESP32: client-esp32 firmware with ILI9341 display over SPI, WiFi networking.
Display test verified on hardware — landscape orientation, text rendering works.

60 workspace tests, all passing.

crates/client-domain/src/render_tree.rs

@@ -0,0 +1,29 @@
+use std::collections::HashMap;
+use domain::WidgetId;
+use crate::BoundingBox;
+
+pub struct RenderTree {
+    pub widget_bounds: HashMap<WidgetId, BoundingBox>,
+}
+
+impl RenderTree {
+    pub fn get_widget_bounds(&self, id: WidgetId) -> Option<&BoundingBox> {
+        self.widget_bounds.get(&id)
+    }
+
+    pub fn diff(&self, other: &RenderTree) -> Vec<WidgetId> {
+        let mut changed = Vec::new();
+        for (id, bounds) in &self.widget_bounds {
+            match other.widget_bounds.get(id) {
+                Some(prev) if prev == bounds => {}
+                _ => changed.push(*id),
+            }
+        }
+        for id in other.widget_bounds.keys() {
+            if !self.widget_bounds.contains_key(id) {
+                changed.push(*id);
+            }
+        }
+        changed
+    }
+}