feat: UI全面改造 + 后端多项修复

【后端修复】
- 删除diet/consultation agent假工具声明
- 修复DayOfWeek实体注释
- 修复Vision API content序列化
- cleanup_service级联删除修复
- 用药提醒时区偏差修复
- 统一DateTime处理(UtcNow+8)
- 新增UTC DateTime JSON转换器

【前端UI重构】
- 配色体系全面更新(#8B5CF6淡紫+#F0ECFF背景)
- 登录页重设计
- 首页重设计(透明顶栏、渐变背景、胶囊输入区)
- 聊天卡片加白蓝边框、渐变标题
- 侧边栏重构(渐变背景、合并顶部、删除底部设置)
- 确认卡片可编辑字段恢复
- 所有子页面加返回按钮
- catch异常加日志
- 删除后refresh provider缓存

backend/src/Health.WebApi/Endpoints/medication_endpoints.cs

@@ -12,12 +12,16 @@ public static class MedicationEndpoints
             var query = db.Medications.Where(m => m.UserId == userId);
             if (filter == "active") query = query.Where(m => m.IsActive);
             else if (filter == "inactive") query = query.Where(m => !m.IsActive);
+            // 北京时间今天对应的 UTC 区间
+            var beijingToday = DateTime.UtcNow.AddHours(8).Date;
+            var todayStartUtc = beijingToday.AddHours(-8);
+            var todayEndUtc = todayStartUtc.AddDays(1);
             var meds = await query.OrderByDescending(m => m.CreatedAt).Select(m => new
             {
                 m.Id, m.Name, m.Dosage, Frequency = m.Frequency.ToString(),
                 m.TimeOfDay, m.StartDate, m.EndDate, m.IsActive, m.Notes,
                 Source = m.Source.ToString(), m.CreatedAt, m.UpdatedAt,
-                todayTaken = m.Logs.Any(l => l.CreatedAt.Date == DateTime.UtcNow.Date && l.Status == MedicationLogStatus.Taken)
+                todayTaken = m.Logs.Any(l => l.CreatedAt >= todayStartUtc && l.CreatedAt < todayEndUtc && l.Status == MedicationLogStatus.Taken)
             }).ToListAsync(ct);
             return Results.Ok(new { code = 0, data = meds, message = (string?)null });
         });
@@ -86,8 +90,10 @@ public static class MedicationEndpoints
         group.MapPost("/{id:guid}/confirm", async (Guid id, HttpContext http, AppDbContext db, CancellationToken ct) =>
         {
             var userId = GetUserId(http);
-            var today = DateOnly.FromDateTime(DateTime.UtcNow);
-            var existing = await db.MedicationLogs.FirstOrDefaultAsync(l => l.MedicationId == id && l.CreatedAt.Date == DateTime.UtcNow.Date && l.Status == MedicationLogStatus.Taken, ct);
+            var beijingToday = DateTime.UtcNow.AddHours(8).Date;
+            var todayStartUtc = beijingToday.AddHours(-8);
+            var todayEndUtc = todayStartUtc.AddDays(1);
+            var existing = await db.MedicationLogs.FirstOrDefaultAsync(l => l.MedicationId == id && l.CreatedAt >= todayStartUtc && l.CreatedAt < todayEndUtc && l.Status == MedicationLogStatus.Taken, ct);
             if (existing != null) {
                 db.MedicationLogs.Remove(existing);
                 await db.SaveChangesAsync(ct);
@@ -96,7 +102,7 @@ public static class MedicationEndpoints
             var log = new MedicationLog
             {
                 Id = Guid.NewGuid(), MedicationId = id, UserId = userId,
-                Status = MedicationLogStatus.Taken, ScheduledTime = TimeOnly.FromDateTime(DateTime.Now), ConfirmedAt = DateTime.UtcNow,
+                Status = MedicationLogStatus.Taken, ScheduledTime = TimeOnly.FromDateTime(DateTime.UtcNow.AddHours(8)), ConfirmedAt = DateTime.UtcNow,
             };
             db.MedicationLogs.Add(log);
             await db.SaveChangesAsync(ct);