feat(esp32-ui): add ESP32 UI firmware base structure

- Add Slint-based ESP32 UI firmware project
- Support ESP32-S3 and ESP32-C3 targets
- Include ST7789 display driver support
- Add touch controller support (XPT2046, FT6X36)
- Include pin configuration and hardware requirements
- Add build scripts and cargo configuration

Co-authored-by: ZeroClaw Agent <zeroclaw_agent@zeroclaw.local>

firmware/zeroclaw-esp32-ui/build.rs

@@ -0,0 +1,14 @@
+use embuild::espidf::sysenv::output;
+
+fn main() {
+    output();
+    slint_build::compile_with_config(
+        "ui/main.slint",
+        slint_build::CompilerConfiguration::new()
+            .embed_resources(slint_build::EmbedResourcesKind::EmbedForSoftwareRenderer)
+            .with_style("material".into()),
+    )
+    .expect("Slint UI compilation failed");
+
+    println!("cargo:rerun-if-changed=ui/");
+}