feat(mobile): UI-01 upload center, capture and auxiliary pages

Co-Authored-By: Claude Code <noreply@anthropic.com>

apps/mobile/lib/pages/login_page.dart

@@ -1,3 +1,12 @@
+/// 登录页（UI-01 §4.5 主题统一，P3 计划 Task 3 基础）。
+///
+/// 账号/密码表单 → [ApiClient.login]（会话由客户端自动持久化到
+/// SessionStore）→ 成功 pushReplacement /home；失败以内联 StateBadge
+/// （图标 + 文案 + 错误色）展示错误码本地化文案（AUTH_RATE_LIMITED 文案
+/// 自带「稍后再试」；网络/校验错误各有专属文案）。提交期间按钮进入
+/// 加载态防重复提交。
+library;
+
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
@@ -6,13 +15,10 @@ import '../core/app_exception.dart';
 import '../core/error_l10n.dart';
 import '../features/uploads/engine_scope.dart';
 import '../l10n/app_localizations.dart';
+import '../ui/components/state_badge.dart';
+import '../ui/tokens.dart';
 
-/// 登录页（P3 计划 Task 3）。
-///
-/// 账号/密码表单 → [ApiClient.login]（会话由客户端自动持久化到
-/// SessionStore）→ 成功 pushReplacement /home；失败按错误码本地化提示
-/// （AUTH_RATE_LIMITED 文案自带「稍后再试」；网络/校验错误各有专属文案）。
-/// 提交期间按钮进入加载态防重复提交。
+/// 登录页。
 class LoginPage extends ConsumerStatefulWidget {
   const LoginPage({super.key});
 
@@ -27,6 +33,9 @@ class _LoginPageState extends ConsumerState<LoginPage> {
 
   bool _submitting = false;
 
+  /// 最近一次提交失败文案（内联 StateBadge 展示；null = 无错误）。
+  String? _errorText;
+
   @override
   void dispose() {
     _accountController.dispose();
@@ -36,9 +45,11 @@ class _LoginPageState extends ConsumerState<LoginPage> {
 
   Future<void> _submit() async {
     if (!_formKey.currentState!.validate()) return;
-    setState(() => _submitting = true);
+    setState(() {
+      _submitting = true;
+      _errorText = null;
+    });
     final l10n = AppLocalizations.of(context);
-    final messenger = ScaffoldMessenger.of(context);
     final navigator = Navigator.of(context);
     try {
       await ref.read(apiClientProvider).login(
@@ -51,13 +62,9 @@ class _LoginPageState extends ConsumerState<LoginPage> {
     } on AppException catch (error) {
       // 429（AUTH_RATE_LIMITED）等文案经错误码映射；登录页的
       // AUTH_INVALID_CREDENTIALS 即「账号或密码错误」。
-      messenger.showSnackBar(
-        SnackBar(content: Text(l10n.messageForError(error))),
-      );
+      if (mounted) setState(() => _errorText = l10n.messageForError(error));
     } on Object {
-      messenger.showSnackBar(
-        SnackBar(content: Text(l10n.errorGeneric)),
-      );
+      if (mounted) setState(() => _errorText = l10n.errorGeneric);
     } finally {
       if (mounted) setState(() => _submitting = false);
     }
@@ -72,7 +79,7 @@ class _LoginPageState extends ConsumerState<LoginPage> {
         child: ConstrainedBox(
           constraints: const BoxConstraints(maxWidth: 420),
           child: Padding(
-            padding: const EdgeInsets.all(24),
+            padding: const EdgeInsets.all(kSpace24),
             child: Form(
               key: _formKey,
               autovalidateMode: AutovalidateMode.onUserInteraction,
@@ -83,16 +90,13 @@ class _LoginPageState extends ConsumerState<LoginPage> {
                   TextFormField(
                     controller: _accountController,
                     autofillHints: const [AutofillHints.username],
-                    decoration: InputDecoration(
-                      labelText: l10n.username,
-                      border: const OutlineInputBorder(),
-                    ),
+                    decoration: InputDecoration(labelText: l10n.username),
                     validator: (value) =>
                         (value == null || value.trim().isEmpty)
                             ? l10n.fieldRequired
                             : null,
                   ),
-                  const SizedBox(height: 16),
+                  const SizedBox(height: kSpace16),
                   TextFormField(
                     controller: _passwordController,
                     obscureText: true,
@@ -100,15 +104,19 @@ class _LoginPageState extends ConsumerState<LoginPage> {
                     autocorrect: false,
                     autofillHints: const [AutofillHints.password],
                     onFieldSubmitted: (_) => _submitting ? null : _submit(),
-                    decoration: InputDecoration(
-                      labelText: l10n.password,
-                      border: const OutlineInputBorder(),
-                    ),
+                    decoration: InputDecoration(labelText: l10n.password),
                     validator: (value) => (value == null || value.isEmpty)
                         ? l10n.fieldRequired
                         : null,
                   ),
-                  const SizedBox(height: 24),
+                  if (_errorText != null) ...[
+                    const SizedBox(height: kSpace16),
+                    StateBadge(
+                      variant: BadgeVariant.error,
+                      label: _errorText!,
+                    ),
+                  ],
+                  const SizedBox(height: kSpace24),
                   FilledButton(
                     onPressed: _submitting ? null : _submit,
                     child: _submitting
@@ -119,7 +127,7 @@ class _LoginPageState extends ConsumerState<LoginPage> {
                           )
                         : Text(l10n.login),
                   ),
-                  const SizedBox(height: 12),
+                  const SizedBox(height: kSpace12),
                   Text(
                     l10n.loginHint,
                     textAlign: TextAlign.center,