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

.gitea/workflows/ci.yml

@@ -0,0 +1,40 @@
+name: CI
+
+on:
+  push:
+    branches: ["*"]
+  pull_request:
+
+jobs:
+  ci:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt, clippy
+
+      - uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+
+      - uses: oven-sh/setup-bun@v2
+
+      - name: Build frontend
+        run: cd painter-js && bun install --frozen-lockfile && bun run build
+
+      - name: Check formatting
+        run: |
+          cargo fmt --all -- --check
+          cd painter-js && bun run fmt:check
+
+      - name: Clippy
+        run: cargo clippy --workspace -- -D warnings
+
+      - name: Tests
+        run: cargo test --workspace