v1.0.0 — Hexagonal architecture rewrite

Restructure the monolithic 252-line main.rs into a 10-crate workspace
with clean hexagonal architecture, swappable adapters, and a production-
ready deployment pipeline.

Backend architecture:
- domain: Canvas, Color/Position/PixelUpdate value objects, port traits
  (CanvasStore, CanvasPersistence, EventBroadcaster), BroadcastEvent
- application: use cases (place_pixel, get_state, save/restore snapshot,
  connect/disconnect), AppState with Arc snapshot cache
- config: AppConfig structs + ConfigSource trait
- api-types: shared DTOs, event name constants
- adapters: config-env, canvas-file, http-axum (rust-embed), socketio,
  websocket — all behind port traits, swappable via feature flags
- server: composition root with graceful shutdown (SIGTERM/SIGINT)

Frontend:
- Transport abstraction: Socket.IO and native WebSocket via VITE_TRANSPORT
- Canvas zoom/pan with mouse wheel, pinch-to-zoom, and +/- buttons
- ImageData rendering (~50x faster than fillRect loop)
- Touch support, responsive CSS scaling, mobile-friendly layout
- OG/Twitter Card meta tags for rich link previews

Production:
- Docker: musl static build on scratch — 2.73MB image
- CI workflows for Gitea and GitHub Actions (fmt, clippy, test, Docker push)
- deploy.sh for private registry
- 39 unit tests across domain and application
- Zero unwraps, zero unsafe, graceful error handling with tracing
- Periodic canvas snapshots with rotation, restored on startup
- All config via environment variables with typed defaults

crates/api-types/src/lib.rs

@@ -0,0 +1,27 @@
+use domain::PixelUpdate;
+use serde::{Deserialize, Serialize};
+
+pub mod events {
+    pub const CANVAS_STATE: &str = "canvas_state";
+    pub const PIXEL_UPDATED: &str = "pixel-updated";
+    pub const PLACE_PIXEL: &str = "place-pixel";
+    pub const CURRENT_SOLDIERS: &str = "current_soldiers";
+    pub const ERROR: &str = "error";
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct PixelUpdatePayload {
+    pub x: u32,
+    pub y: u32,
+    pub color: u32,
+}
+
+impl From<PixelUpdate> for PixelUpdatePayload {
+    fn from(update: PixelUpdate) -> Self {
+        Self {
+            x: update.position().x(),
+            y: update.position().y(),
+            color: update.color().as_u32(),
+        }
+    }
+}