feat(ui): 登录页重设计并统一弹框主题渐变外壳

lib/pages/auth/auth_widgets.dart

@@ -70,52 +70,45 @@ class _AuthCard extends StatelessWidget {
   Widget build(BuildContext context) {
     final l10n = state.l10n;
     final status = state.status;
-    return Container(
+    // 不再做卡片盒子，表单直接排在红光晕背景上。
+    return Column(
       key: const Key('auth-card'),
-      padding: const EdgeInsets.all(_cardPadding),
-      decoration: BoxDecoration(
-        color: AppColors.card,
-        borderRadius: BorderRadius.circular(_cardRadius),
-        border: Border.all(color: AppColors.border),
-      ),
-      child: Column(
-        crossAxisAlignment: CrossAxisAlignment.stretch,
-        children: [
-          _AuthModeSwitch(
-            l10n: l10n,
-            signUpMode: status.signUpMode,
-            busy: status.busy,
-            onSelected: callbacks.onModeSelected,
+      crossAxisAlignment: CrossAxisAlignment.stretch,
+      children: [
+        _AuthModeSwitch(
+          l10n: l10n,
+          signUpMode: status.signUpMode,
+          busy: status.busy,
+          onSelected: callbacks.onModeSelected,
+        ),
+        const SizedBox(height: 24),
+        Text(
+          status.signUpMode ? l10n.authSignUpTitle : l10n.authSignInTitle,
+          style: const TextStyle(
+            color: AppColors.onSurface,
+            fontSize: 24,
+            fontWeight: FontWeight.w600,
+            height: 1.2,
           ),
-          const SizedBox(height: 22),
-          Text(
-            status.signUpMode ? l10n.authSignUpTitle : l10n.authSignInTitle,
-            style: const TextStyle(
-              color: AppColors.onSurface,
-              fontSize: 25,
-              fontWeight: FontWeight.w800,
-              height: 1.2,
-            ),
+        ),
+        const SizedBox(height: 6),
+        Text(
+          status.signUpMode ? l10n.authSignUpSubtitle : l10n.authSubtitle,
+          style: const TextStyle(
+            color: AppColors.muted,
+            fontSize: AppDimens.body,
+            height: 1.45,
           ),
-          const SizedBox(height: 6),
-          Text(
-            status.signUpMode ? l10n.authSignUpSubtitle : l10n.authSubtitle,
-            style: const TextStyle(
-              color: AppColors.muted,
-              fontSize: AppDimens.body,
-              height: 1.45,
-            ),
-          ),
-          const SizedBox(height: 22),
-          _AuthFields(state: state, callbacks: callbacks),
-          if (status.errorMessage != null) ...[
-            const SizedBox(height: 14),
-            _AuthError(message: status.errorMessage!),
-          ],
-          const SizedBox(height: 22),
-          _AuthSubmitButton(state: state, onSubmit: callbacks.onSubmit),
+        ),
+        const SizedBox(height: 20),
+        _AuthFields(state: state, callbacks: callbacks),
+        if (status.errorMessage != null) ...[
+          const SizedBox(height: 14),
+          _AuthError(message: status.errorMessage!),
         ],
-      ),
+        const SizedBox(height: 22),
+        _AuthSubmitButton(state: state, onSubmit: callbacks.onSubmit),
+      ],
     );
   }
 }
@@ -135,47 +128,23 @@ class _AuthModeSwitch extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return TextButton(
+    return Row(
       key: const Key('auth-switch-mode'),
-      onPressed: busy ? null : () => onSelected(!signUpMode),
-      style: TextButton.styleFrom(
-        minimumSize: const Size(0, _minTapTarget),
-        padding: EdgeInsets.zero,
-        overlayColor: AppColors.transparent,
-        splashFactory: NoSplash.splashFactory,
-        shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(22)),
-      ),
-      child: Container(
-        height: 36,
-        padding: const EdgeInsets.all(2),
-        decoration: BoxDecoration(
-          color: AppColors.raised,
-          borderRadius: BorderRadius.circular(18),
+      children: [
+        _ModeTab(
+          segmentKey: const Key('auth-mode-sign-in'),
+          label: l10n.signIn,
+          selected: !signUpMode,
+          onTap: busy ? null : () => onSelected(false),
         ),
-        child: Row(
-          children: [
-            Expanded(
-              child: _ModeSegment(
-                segmentKey: const Key('auth-mode-sign-in'),
-                label: l10n.signIn,
-                hiddenLabel: l10n.authSwitchToSignIn,
-                selected: !signUpMode,
-                onTap: busy ? null : () => onSelected(false),
-              ),
-            ),
-            const SizedBox(width: 4),
-            Expanded(
-              child: _ModeSegment(
-                segmentKey: const Key('auth-mode-sign-up'),
-                label: l10n.signUp,
-                hiddenLabel: l10n.authSwitchToSignUp,
-                selected: signUpMode,
-                onTap: busy ? null : () => onSelected(true),
-              ),
-            ),
-          ],
+        const SizedBox(width: AppDimens.followingSegmentGap),
+        _ModeTab(
+          segmentKey: const Key('auth-mode-sign-up'),
+          label: l10n.signUp,
+          selected: signUpMode,
+          onTap: busy ? null : () => onSelected(true),
         ),
-      ),
+      ],
     );
   }
 }