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/entities/mod.rs

@@ -0,0 +1,7 @@
+mod widget_config;
+mod data_source;
+mod layout_preset;
+
+pub use widget_config::{WidgetConfig, WidgetId};
+pub use data_source::{DataSource, DataSourceId, DataSourceType, DataSourceConfig, DataSourceValidationError};
+pub use layout_preset::{LayoutPreset, LayoutPresetId};