feat: AI 意图路由/草稿存储 + Prompts 模块化 + UI 视觉统一 + AI 同意门 + 资源更新

后端:
- 新增 ai_intent_router 意图路由
- 新增 AiEntryDraft 草稿存储 + EF 迁移
- 新增 Prompts 模块化（global/modules/rag/router）
- AI Agent handlers 扩展

前端:
- 新增 AI 同意门 (ai_consent_gate/provider/details_page)
- HealthMetricVisuals 视觉统一
- 设备扫描/管理页面优化
- agent 插图替换 + 趋势指标图标

配置:
- DeepSeek 模型改 deepseek-v4-flash
- .gitignore 加 artifacts/audit
- build.gradle.kts 签名配置调整

health_app/lib/widgets/authenticated_network_image.dart

@@ -7,6 +7,9 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../core/api_client.dart' show baseUrl;
 import '../providers/auth_provider.dart';
 
+const int _maxProtectedImageCacheEntries = 32;
+final Map<String, Uint8List> _protectedImageBytesCache = {};
+
 String protectedMediaUrl(String value) {
   final trimmed = value.trim();
   if (trimmed.isEmpty) return trimmed;
@@ -58,6 +61,7 @@ class _AuthenticatedNetworkImageState
     extends ConsumerState<AuthenticatedNetworkImage> {
   late String _resolvedUrl;
   Future<Uint8List>? _bytes;
+  Uint8List? _cachedBytes;
 
   @override
   void initState() {
@@ -73,11 +77,21 @@ class _AuthenticatedNetworkImageState
 
   void _configure() {
     _resolvedUrl = protectedMediaUrl(widget.imageUrl);
-    _bytes = mediaRequiresAuthentication(_resolvedUrl)
-        ? _loadProtectedBytes(_resolvedUrl)
+    _cachedBytes = _protectedImageBytesCache[_resolvedUrl];
+    _bytes = mediaRequiresAuthentication(_resolvedUrl) && _cachedBytes == null
+        ? _loadAndCacheProtectedBytes(_resolvedUrl)
         : null;
   }
 
+  Future<Uint8List> _loadAndCacheProtectedBytes(String url) async {
+    final data = await _loadProtectedBytes(url);
+    if (_protectedImageBytesCache.length >= _maxProtectedImageCacheEntries) {
+      _protectedImageBytesCache.remove(_protectedImageBytesCache.keys.first);
+    }
+    _protectedImageBytesCache[url] = data;
+    return data;
+  }
+
   Future<Uint8List> _loadProtectedBytes(String url) async {
     final response = await ref
         .read(apiClientProvider)
@@ -91,6 +105,18 @@ class _AuthenticatedNetworkImageState
 
   @override
   Widget build(BuildContext context) {
+    final cachedBytes = _cachedBytes;
+    if (cachedBytes != null) {
+      return Image.memory(
+        cachedBytes,
+        fit: widget.fit,
+        width: widget.width,
+        height: widget.height,
+        gaplessPlayback: true,
+        errorBuilder: widget.errorBuilder,
+      );
+    }
+
     final bytes = _bytes;
     if (bytes == null) {
       return Image.network(
@@ -98,6 +124,7 @@ class _AuthenticatedNetworkImageState
         fit: widget.fit,
         width: widget.width,
         height: widget.height,
+        gaplessPlayback: true,
         loadingBuilder: widget.loadingBuilder,
         errorBuilder: widget.errorBuilder,
       );
@@ -123,6 +150,7 @@ class _AuthenticatedNetworkImageState
           fit: widget.fit,
           width: widget.width,
           height: widget.height,
+          gaplessPlayback: true,
           errorBuilder: widget.errorBuilder,
         );
       },