feat(client): 商品详情页图片支持双击全屏查看

抽出共享全屏查看器 fullscreen_image_viewer.dart（复用扫码页的
InteractiveViewer+PageView+黑底 modal），详情页缩略图双击打开，
扫码公开页改为复用同一组件去重。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/lib/screens/products/product_detail_screen.dart

@@ -9,6 +9,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../../core/config/app_config.dart';
 import '../../core/utils/print_util.dart';
 import '../../widgets/label_preview_dialog.dart';
+import '../../widgets/fullscreen_image_viewer.dart';
 import '../../widgets/write_guard.dart';
 import '../../core/theme/app_theme.dart';
 import '../../models/product.dart';
@@ -309,9 +310,16 @@ class _ProductDetailScreenState extends ConsumerState<ProductDetailScreen> {
           height: 120,
           child: Row(
             children: [
-              ...p.images.map((img) => _ImageThumbnail(
-                    url: AppConfig.baseUrl + img.url,
-                    onDelete: () => _deleteImage(img),
+              ...p.images.asMap().entries.map((e) => _ImageThumbnail(
+                    url: AppConfig.baseUrl + e.value.url,
+                    onDelete: () => _deleteImage(e.value),
+                    onView: () => showFullscreenImages(
+                      context,
+                      p.images
+                          .map((img) => AppConfig.baseUrl + img.url)
+                          .toList(),
+                      initialIndex: e.key,
+                    ),
                   )),
               if (p.images.length < 5)
                 WriteGuard(
@@ -567,7 +575,9 @@ class _ProductDetailScreenState extends ConsumerState<ProductDetailScreen> {
 class _ImageThumbnail extends StatelessWidget {
   final String url;
   final VoidCallback onDelete;
-  const _ImageThumbnail({required this.url, required this.onDelete});
+  final VoidCallback onView;
+  const _ImageThumbnail(
+      {required this.url, required this.onDelete, required this.onView});
 
   @override
   Widget build(BuildContext context) {
@@ -575,19 +585,22 @@ class _ImageThumbnail extends StatelessWidget {
       padding: const EdgeInsets.only(right: 8),
       child: Stack(
         children: [
-          ClipRRect(
-            borderRadius: BorderRadius.circular(4),
-            child: Image.network(
-              url,
-              width: 110,
-              height: 110,
-              fit: BoxFit.cover,
-              errorBuilder: (_, __, ___) => Container(
+          GestureDetector(
+            onDoubleTap: onView,
+            child: ClipRRect(
+              borderRadius: BorderRadius.circular(4),
+              child: Image.network(
+                url,
                 width: 110,
                 height: 110,
-                color: AppTheme.border,
-                child: const Icon(Icons.broken_image,
-                    color: AppTheme.textSecondary),
+                fit: BoxFit.cover,
+                errorBuilder: (_, __, ___) => Container(
+                  width: 110,
+                  height: 110,
+                  color: AppTheme.border,
+                  child: const Icon(Icons.broken_image,
+                      color: AppTheme.textSecondary),
+                ),
               ),
             ),
           ),

client/lib/screens/public/public_product_screen.dart

@@ -6,6 +6,7 @@ import 'package:flutter/services.dart';
 import 'package:go_router/go_router.dart';
 import 'package:url_launcher/url_launcher.dart';
 import '../../core/config/app_config.dart';
+import '../../widgets/fullscreen_image_viewer.dart';
 
 // ── Palette & typography constants ────────────────────────────────────
 const _kPaper = Color(0xFFFAF8F5);
@@ -476,12 +477,7 @@ class _HeroGalleryState extends State<_HeroGallery> {
   }
 
   void _openFullscreen(int index) {
-    Navigator.of(context).push(PageRouteBuilder(
-      opaque: false,
-      barrierColor: Colors.black87,
-      pageBuilder: (_, __, ___) => _FullscreenViewer(
-        urls: widget.imageUrls, initialIndex: index),
-    ));
+    showFullscreenImages(context, widget.imageUrls, initialIndex: index);
   }
 }
 
@@ -534,66 +530,6 @@ class _GlassChip extends StatelessWidget {
   }
 }
 
-// ── Full-screen image viewer ──────────────────────────────────────────
-
-class _FullscreenViewer extends StatefulWidget {
-  final List<String> urls;
-  final int initialIndex;
-  const _FullscreenViewer({required this.urls, required this.initialIndex});
-
-  @override
-  State<_FullscreenViewer> createState() => _FullscreenViewerState();
-}
-
-class _FullscreenViewerState extends State<_FullscreenViewer> {
-  late PageController _ctrl;
-
-  @override
-  void initState() {
-    super.initState();
-    _ctrl = PageController(initialPage: widget.initialIndex);
-  }
-
-  @override
-  void dispose() { _ctrl.dispose(); super.dispose(); }
-
-  @override
-  Widget build(BuildContext context) {
-    return GestureDetector(
-      onTap: () => Navigator.of(context).pop(),
-      child: Scaffold(
-        backgroundColor: Colors.transparent,
-        body: Stack(
-          children: [
-            PageView.builder(
-              controller: _ctrl,
-              itemCount: widget.urls.length,
-              itemBuilder: (_, i) => Center(
-                child: InteractiveViewer(
-                  child: Image.network(widget.urls[i], fit: BoxFit.contain,
-                      errorBuilder: (_, __, ___) =>
-                          const Icon(Icons.broken_image, size: 64, color: Colors.white54)),
-                )),
-            ),
-            Positioned(
-              top: 40, right: 16,
-              child: GestureDetector(
-                onTap: () => Navigator.of(context).pop(),
-                child: Container(
-                  padding: const EdgeInsets.all(8),
-                  decoration: BoxDecoration(
-                    color: Colors.black54, borderRadius: BorderRadius.circular(20)),
-                  child: const Icon(Icons.close, color: Colors.white, size: 20),
-                ),
-              ),
-            ),
-          ],
-        ),
-      ),
-    );
-  }
-}
-
 // ── Verified Ribbon ───────────────────────────────────────────────────
 
 class _VerifiedRibbon extends StatelessWidget {

client/lib/widgets/fullscreen_image_viewer.dart

@@ -0,0 +1,86 @@
+import 'package:flutter/material.dart';
+
+/// 全屏图片查看器：黑底 modal + 多图左右翻页（PageView）+ 双指缩放/拖拽（InteractiveViewer）。
+/// 点击背景或右上角关闭按钮退出。纯 Flutter 内置组件，无需额外依赖。
+///
+/// 用法：
+/// ```dart
+/// showFullscreenImages(context, urls, initialIndex: 2);
+/// ```
+void showFullscreenImages(BuildContext context, List<String> urls,
+    {int initialIndex = 0}) {
+  if (urls.isEmpty) return;
+  Navigator.of(context).push(PageRouteBuilder(
+    opaque: false,
+    barrierColor: Colors.black87,
+    pageBuilder: (_, __, ___) =>
+        FullscreenImageViewer(urls: urls, initialIndex: initialIndex),
+  ));
+}
+
+class FullscreenImageViewer extends StatefulWidget {
+  final List<String> urls;
+  final int initialIndex;
+  const FullscreenImageViewer(
+      {super.key, required this.urls, this.initialIndex = 0});
+
+  @override
+  State<FullscreenImageViewer> createState() => _FullscreenImageViewerState();
+}
+
+class _FullscreenImageViewerState extends State<FullscreenImageViewer> {
+  late PageController _ctrl;
+
+  @override
+  void initState() {
+    super.initState();
+    _ctrl = PageController(initialPage: widget.initialIndex);
+  }
+
+  @override
+  void dispose() {
+    _ctrl.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      onTap: () => Navigator.of(context).pop(),
+      child: Scaffold(
+        backgroundColor: Colors.transparent,
+        body: Stack(
+          children: [
+            PageView.builder(
+              controller: _ctrl,
+              itemCount: widget.urls.length,
+              itemBuilder: (_, i) => Center(
+                child: InteractiveViewer(
+                  child: Image.network(widget.urls[i], fit: BoxFit.contain,
+                      errorBuilder: (_, __, ___) => const Icon(
+                          Icons.broken_image,
+                          size: 64,
+                          color: Colors.white54)),
+                ),
+              ),
+            ),
+            Positioned(
+              top: 40,
+              right: 16,
+              child: GestureDetector(
+                onTap: () => Navigator.of(context).pop(),
+                child: Container(
+                  padding: const EdgeInsets.all(8),
+                  decoration: BoxDecoration(
+                      color: Colors.black54,
+                      borderRadius: BorderRadius.circular(20)),
+                  child: const Icon(Icons.close, color: Colors.white, size: 20),
+                ),
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}