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/domain/src/value_objects/value.rs

@@ -0,0 +1,58 @@
+use std::collections::BTreeMap;
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Value {
+    Null,
+    Bool(bool),
+    Number(f64),
+    String(String),
+    Array(Vec<Value>),
+    Object(BTreeMap<String, Value>),
+}
+
+impl Value {
+    pub fn estimated_size(&self) -> usize {
+        match self {
+            Value::Null | Value::Bool(_) => 1,
+            Value::Number(_) => 8,
+            Value::String(s) => s.len(),
+            Value::Array(arr) => arr.iter().map(|v| v.estimated_size()).sum(),
+            Value::Object(map) => map
+                .iter()
+                .map(|(k, v)| k.len() + v.estimated_size())
+                .sum(),
+        }
+    }
+
+    pub fn get_path(&self, path: &str) -> Option<&Value> {
+        let path = path.strip_prefix("$").unwrap_or(path);
+        let mut current = self;
+
+        for raw_segment in path.split('.').filter(|s| !s.is_empty()) {
+            if let Some(bracket_pos) = raw_segment.find('[') {
+                let key = &raw_segment[..bracket_pos];
+                let index_str = raw_segment[bracket_pos + 1..].strip_suffix(']')?;
+                let index: usize = index_str.parse().ok()?;
+
+                if !key.is_empty() {
+                    match current {
+                        Value::Object(map) => current = map.get(key)?,
+                        _ => return None,
+                    }
+                }
+
+                match current {
+                    Value::Array(arr) => current = arr.get(index)?,
+                    _ => return None,
+                }
+            } else {
+                match current {
+                    Value::Object(map) => current = map.get(raw_segment)?,
+                    _ => return None,
+                }
+            }
+        }
+
+        Some(current)
+    }
+}