Add demo trading page, trader snapshot service and trading tables

Add trading_symbols, trading_analyses, trading_orders and trading_events.
The new trader service publishes account, position and open-order
snapshots of the Binance demo account to Redis every 3s. The /trading
page shows engine status, start/stop, balances, positions, the symbol
list with angle selection, open orders and the event timeline.

web/src/pages/trading/components/AddSymbolDialog.vue

@@ -0,0 +1,70 @@
+<script lang="ts" setup>
+import type { Angle, SymbolOption } from "@/apis/trading"
+import { addSymbol, ANGLE_LABELS, listSymbolOptions } from "@/apis/trading"
+
+const emit = defineEmits<{ added: [symbol: string] }>()
+const visible = defineModel<boolean>({ required: true })
+
+const symbol = ref("")
+const angle = ref<Angle>("long")
+const symbolOptions = ref<SymbolOption[]>([])
+const loading = ref(false)
+const submitting = ref(false)
+
+const options = computed(() => symbolOptions.value.map(s => ({ value: s.symbol, label: `${s.base}/USDT 永续` })))
+
+watch(visible, async (open) => {
+  if (!open)
+    return
+  symbol.value = ""
+  loading.value = true
+  try {
+    symbolOptions.value = await listSymbolOptions()
+  } finally {
+    loading.value = false
+  }
+}, { immediate: true })
+
+async function submit() {
+  submitting.value = true
+  try {
+    await addSymbol(symbol.value, angle.value)
+    ElMessage.success(`已加入 ${symbol.value}`)
+    emit("added", symbol.value)
+    visible.value = false
+  } finally {
+    submitting.value = false
+  }
+}
+</script>
+
+<template>
+  <el-dialog v-model="visible" title="新增交易币种" width="480px">
+    <el-form label-width="64px">
+      <el-form-item label="币种">
+        <el-select-v2
+          v-model="symbol" :options="options" :loading="loading" filterable placeholder="搜索，如 BTCUSDT"
+          class="w-full"
+        />
+        <div class="text-xs text-[var(--el-text-color-secondary)]">
+          只列出模拟盘和实盘都在交易的加密货币 USDT 永续合约
+        </div>
+      </el-form-item>
+      <el-form-item label="角度">
+        <el-radio-group v-model="angle">
+          <el-radio v-for="(label, value) in ANGLE_LABELS" :key="value" :value="value">
+            {{ label }}
+          </el-radio>
+        </el-radio-group>
+      </el-form-item>
+    </el-form>
+    <template #footer>
+      <el-button @click="visible = false">
+        取消
+      </el-button>
+      <el-button type="primary" :disabled="!symbol" :loading="submitting" @click="submit">
+        加入
+      </el-button>
+    </template>
+  </el-dialog>
+</template>