ems-core v1.0.0: Standard EMS platform core

Shared backend + frontend for multi-customer EMS deployments.
- 12 enterprise modules: quota, cost, charging, maintenance, analysis, etc.
- 120+ API endpoints, 37 database tables
- Customer config mechanism (CUSTOMER env var + YAML config)
- Collectors: Modbus TCP, MQTT, HTTP API, Sungrow iSolarCloud
- Frontend: React 19 + Ant Design + ECharts + Three.js
- Infrastructure: Redis cache, rate limiting, aggregation engine

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/public/devices/default.svg

@@ -0,0 +1,19 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="400" height="300" viewBox="0 0 400 300">
+  <defs>
+    <linearGradient id="bg" x1="0%" y1="0%" x2="100%" y2="100%">
+      <stop offset="0%" style="stop-color:#1e293b;stop-opacity:1" />
+      <stop offset="100%" style="stop-color:#0f172a;stop-opacity:1" />
+    </linearGradient>
+  </defs>
+  <rect width="400" height="300" fill="url(#bg)" rx="12"/>
+  <!-- Device icon -->
+  <rect x="150" y="60" width="100" height="120" rx="8" fill="none" stroke="#64748b" stroke-width="3"/>
+  <circle cx="200" cy="110" r="25" fill="none" stroke="#64748b" stroke-width="2"/>
+  <path d="M 185 110 L 200 95 L 215 110 L 200 125 Z" fill="#64748b" opacity="0.5"/>
+  <!-- Signal -->
+  <line x1="200" y1="60" x2="200" y2="40" stroke="#64748b" stroke-width="2"/>
+  <circle cx="200" cy="36" r="4" fill="#64748b"/>
+  <!-- Label -->
+  <text x="200" y="228" text-anchor="middle" fill="#94a3b8" font-family="Arial, sans-serif" font-size="20" font-weight="bold">IoT Device</text>
+  <text x="200" y="248" text-anchor="middle" fill="#6b7280" font-family="Arial, sans-serif" font-size="12">通用设备</text>
+</svg>