CUB-119: Add docker-compose.yml + .env.example, remove legacy .NET backend and Angular frontend

.env.example

@@ -0,0 +1,33 @@
+# =============================================================================
+# Control Center — Environment Configuration Template
+# =============================================================================
+# Copy this file to `.env` and fill in real values.
+# Never commit `.env` — it is in .gitignore by default.
+# =============================================================================
+
+# ── Database ────────────────────────────────────────────────────────────────
+POSTGRES_DB=controlcenter
+POSTGRES_USER=controlcenter
+POSTGRES_PASSWORD=changeme
+POSTGRES_PORT=5432
+
+# ── Backend ───────────────────────────────────────────────────────────────────
+BACKEND_PORT=8080
+LOG_LEVEL=info
+ENVIRONMENT=development
+
+# ── Frontend ────────────────────────────────────────────────────────────────
+FRONTEND_PORT=3000
+
+# ── CORS ────────────────────────────────────────────────────────────────────
+# Comma-separated allowed origins.  Use "*" for local dev.
+CORS_ORIGIN=http://localhost:3000
+
+# ── OpenClaw Gateway ──────────────────────────────────────────────────────────
+# URL to the OpenClaw gateway agent status endpoint.
+# In Docker Compose, use the container name or host.docker.internal for the
+# gateway running outside Compose.
+GATEWAY_URL=http://host.docker.internal:18789/api/agents
+
+# How often to poll the gateway for agent state updates.
+GATEWAY_POLL_INTERVAL=5s