feat(admin): implement initial admin dashboard and member management

This commit introduces the foundational structure for the admin dashboard, focusing on the member management feature.
Key additions include:

- A new page at `/admin/manage/members` to display and manage members.
- An `AddModal` component with a comprehensive form for creating new members, featuring validation with Zod and input
masking.
- A reusable `PhoneInput` component with country code selection, backed by a new `useCountries` composable and a full
country dataset.
- A custom, user-friendly global error page (`error.vue`) to handle application errors gracefully.
- Updated dashboard sidebar navigation to include the new member management section.
- Added recommended VS Code extensions and settings to improve developer experience.

app/components/PhoneInput.vue

@@ -0,0 +1,64 @@
+<!-- ~/components/PhoneInput.vue -->
+<script setup lang="ts">
+import { USelectMenu, UInput } from "#components";
+import { useCountries } from "~/composables/useCountries";
+
+interface Props {
+  modelValue?: string;
+  defaultDial?: string;
+}
+
+const props = defineProps<Props>();
+const emit = defineEmits(["update:modelValue", "update:country"]);
+
+const { getAll } = useCountries();
+
+// 当前选中国家
+const selectedCountry = ref(
+  getAll().find((c) => c.dial === props.defaultDial)?.dial || getAll()[0]?.dial
+);
+
+console.table(getAll().map(c => ({ name: c.name.cn, dial: c.dial })));
+
+// 用户输入的电话号码
+const phone = ref(props.modelValue || "");
+
+// 计算选项
+const countryOptions = computed(() =>
+  getAll()
+    .filter((c) => c.dial && c.dial.trim() !== "")
+    .map((c) => ({
+      label: `${c.name.cn} (${c.dial || "未知"})`,
+      id: c.dial || "unknown",
+    }))
+);
+
+// 完整号码输出
+const fullNumber = computed(() => {
+  const dial = selectedCountry.value || "";
+  return `${dial}${phone.value}`;
+});
+
+// 双向绑定
+watch(phone, () => emit("update:modelValue", fullNumber.value));
+watch(selectedCountry, () => emit("update:country", selectedCountry.value));
+</script>
+
+<template>
+  <div class="flex items-center gap-2">
+    <!-- 国家区号选择 -->
+    <USelectMenu
+      v-model="selectedCountry"
+      value-key="id"
+      :items="countryOptions"
+    />
+
+    <!-- 电话号码输入 -->
+    <UInput
+      v-model="phone"
+      placeholder="输入电话号码"
+      type="tel"
+      class="flex-1"
+    />
+  </div>
+</template>