feat: add full workbench login page

apps/web/src/features/auth/ServerLogin.svelte

@@ -1,16 +1,11 @@
 <script lang="ts">
-  import { createEventDispatcher } from 'svelte';
-
   export let apiBase: string;
+  export let onLogin: (detail: { apiBase: string; account: string }) => void = () => {};
 
-  const dispatch = createEventDispatcher<{ serverChange: { apiBase: string } }>();
   let server = apiBase;
-
-  function saveServer() {
-    const normalized = normalizeServer(server);
-    server = normalized;
-    dispatch('serverChange', { apiBase: normalized });
-  }
+  let account = '';
+  let password = '';
+  let error = '';
 
   function normalizeServer(value: string) {
     const trimmed = value.trim();
@@ -19,10 +14,50 @@
     }
     return `http://${trimmed}`;
   }
+
+  function submitLogin() {
+    error = '';
+    if (!account.trim() || !password.trim()) {
+      error = 'Enter an account and password.';
+      return;
+    }
+
+    const normalized = normalizeServer(server);
+    server = normalized;
+    onLogin({ apiBase: normalized, account: account.trim() });
+  }
 </script>
 
-<form aria-label="服务器登录" class="server-login" on:submit|preventDefault={saveServer}>
-  <label for="server-address">服务器 IP 或域名</label>
-  <input id="server-address" name="server" bind:value={server} placeholder="http://localhost:8080" />
-  <button type="submit">保存服务器</button>
-</form>
+<main class="login-page">
+  <section class="login-panel" aria-labelledby="login-title">
+    <div class="login-brand" aria-hidden="true">SA</div>
+    <div class="login-heading">
+      <p>Private workbench</p>
+      <h1 id="login-title">SenlinAI Workbench</h1>
+    </div>
+
+    <form class="server-login" aria-label="Server login" on:submit|preventDefault={submitLogin}>
+      <label for="server-address">Server IP or domain</label>
+      <input id="server-address" name="server" bind:value={server} placeholder="http://localhost:8080" />
+
+      <label for="login-account">Email or username</label>
+      <input id="login-account" name="account" bind:value={account} autocomplete="username" />
+
+      <label for="login-password">Password</label>
+      <input
+        id="login-password"
+        name="password"
+        type="password"
+        bind:value={password}
+        autocomplete="current-password"
+      />
+
+      {#if error}
+        <p class="form-error" aria-live="polite">{error}</p>
+      {/if}
+
+      <button type="submit">Log in</button>
+      <p class="login-note">The server address is remembered on this device.</p>
+    </form>
+  </section>
+</main>