add Dockerfile + docker-compose: single-image deploy (nginx + backend)

Multi-stage build: node builds frontend dist, golang builds static
binary (modernc sqlite, CGO off), alpine runtime runs nginx :80 +
backend :8890 in one container. nginx serves SPA with fallback, strips
/api prefix (same as vite dev proxy), proxies protocol endpoints
(/mcp, /m/*, /v1/*, /d/*, /ws/*, *.php) with buffering off for
NDJSON/SSE streams and WS upgrade headers.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

.dockerignore

@@ -0,0 +1,14 @@
+.git
+node_modules
+frontend/node_modules
+frontend/dist
+backend/data
+backend/cyibox
+docs
+*.log
+*.db
+*.db-shm
+*.db-wal
+.dockerignore
+Dockerfile
+docker-compose.yml