feat: add web deployment with axum server, Docker support, and browser UI

Introduce src-web (axum HTTP server) exposing all 43 database operations
as REST APIs with SSE streaming for AI, transfers, and SQL file execution.
Frontend adapts automatically between Tauri and HTTP backends via api.ts.
Includes password authentication, Docker packaging, and login page.

src/components/auth/LoginPage.vue

@@ -0,0 +1,57 @@
+<script setup lang="ts">
+import { ref } from "vue";
+import { Button } from "@/components/ui/button";
+import { Input } from "@/components/ui/input";
+import { DatabaseZap } from "lucide-vue-next";
+
+const emit = defineEmits<{ authenticated: [] }>();
+
+const password = ref("");
+const error = ref("");
+const loading = ref(false);
+
+async function login() {
+  loading.value = true;
+  error.value = "";
+  try {
+    const res = await fetch("/api/auth/login", {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ password: password.value }),
+    });
+    if (res.ok) {
+      emit("authenticated");
+    } else {
+      const text = await res.text();
+      error.value = text || "密码错误";
+    }
+  } catch (e: any) {
+    error.value = e?.message || "连接失败";
+  } finally {
+    loading.value = false;
+  }
+}
+</script>
+
+<template>
+  <div class="flex items-center justify-center h-screen bg-background">
+    <div class="w-80 space-y-6 text-center">
+      <div class="flex items-center justify-center gap-2 text-2xl font-bold">
+        <DatabaseZap class="w-8 h-8" />
+        <span>DBX</span>
+      </div>
+      <form class="space-y-4" @submit.prevent="login">
+        <Input
+          v-model="password"
+          type="password"
+          placeholder="请输入访问密码"
+          autofocus
+        />
+        <p v-if="error" class="text-sm text-destructive">{{ error }}</p>
+        <Button type="submit" class="w-full" :disabled="loading || !password">
+          {{ loading ? "登录中..." : "登录" }}
+        </Button>
+      </form>
+    </div>
+  </div>
+</template>