主要变更：

新增统一缓存封装：[AppCache.cs (line 12)](/E:/jiaowu/src/Jiaowu.Api/Infrastructure/Caching/AppCache.cs:12)
接入 HybridCache 和可选 Redis：[Program.cs (line 153)](/E:/jiaowu/src/Jiaowu.Api/Program.cs:153)
缓存学生激活选项、基础数据、公开课表和课表选项。
个人课表、选课容量、成绩、权限、通知和任务状态保持实时查询。
基础数据、课程、教师、教学任务、作息、考试和课表发布后自动失效相关缓存。
新增 /health/cache，Redis 故障不影响 /health/ready。
Compose 增加 256MB、allkeys-lfu、无持久化的 redis:8.8-alpine 服务；该镜像标签已由 Docker 官方镜像仓库核对。
更新 [.env.example (line 1)](/E:/jiaowu/.env.example:1) 和 [README.md (line 190)](/E:/jiaowu/README.md:190) 部署说明。

src/Jiaowu.Api/Program.cs

@@ -3,6 +3,7 @@ using System.Text.Json.Serialization;
 using Jiaowu.Api.Domain.Identity;
 using Jiaowu.Api.Infrastructure.Configuration;
 using Jiaowu.Api.Infrastructure.Auth;
+using Jiaowu.Api.Infrastructure.Caching;
 using Jiaowu.Api.Infrastructure.Exams;
 using Jiaowu.Api.Infrastructure.Middleware;
 using Jiaowu.Api.Infrastructure.Persistence;
@@ -12,6 +13,7 @@ using Microsoft.AspNetCore.Authentication.JwtBearer;
 using Microsoft.AspNetCore.RateLimiting;
 using Microsoft.Data.Sqlite;
 using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Caching.Distributed;
 using Microsoft.IdentityModel.Tokens;
 using Microsoft.OpenApi.Models;
 using System.Threading.RateLimiting;
@@ -61,6 +63,9 @@ if (seedDemoData && builder.Environment.IsDevelopment())
 var databaseOptions = builder.Configuration
     .GetSection(DatabaseOptions.SectionName)
     .Get<DatabaseOptions>() ?? new DatabaseOptions();
+var cacheOptions = builder.Configuration
+    .GetSection(AppCacheOptions.SectionName)
+    .Get<AppCacheOptions>() ?? new AppCacheOptions();
 
 if (databaseOptions.Provider.Equals("SQLite", StringComparison.OrdinalIgnoreCase) &&
     !builder.Environment.IsDevelopment())
@@ -82,7 +87,24 @@ if (databaseOptions.CommandTimeoutSeconds is < 5 or > 300)
         "Database:CommandTimeoutSeconds 必须在 5 到 300 秒之间。");
 }
 
+if (cacheOptions.ReferenceExpirationMinutes is < 1 or > 1440 ||
+    cacheOptions.TimetableExpirationMinutes is < 1 or > 1440 ||
+    cacheOptions.ReferenceLocalExpirationSeconds is < 1 or > 3600 ||
+    cacheOptions.TimetableLocalExpirationSeconds is < 1 or > 3600 ||
+    cacheOptions.MaximumPayloadKilobytes is < 64 or > 16384 ||
+    cacheOptions.ReferenceLocalExpirationSeconds >
+        cacheOptions.ReferenceExpirationMinutes * 60 ||
+    cacheOptions.TimetableLocalExpirationSeconds >
+        cacheOptions.TimetableExpirationMinutes * 60 ||
+    string.IsNullOrWhiteSpace(cacheOptions.KeyPrefix) ||
+    cacheOptions.KeyPrefix.Length > 100)
+{
+    throw new InvalidOperationException(
+        "Cache 缓存时间或 MaximumPayloadKilobytes 超出允许范围。");
+}
+
 builder.Services.AddSingleton(databaseOptions);
+builder.Services.AddSingleton(cacheOptions);
 builder.Services.AddDbContextPool<AppDbContext>(options =>
 {
     if (databaseOptions.Provider.Equals("SQLite", StringComparison.OrdinalIgnoreCase))
@@ -125,6 +147,19 @@ builder.Services.AddDbContextPool<AppDbContext>(options =>
     });
 });
 
+var redisConnectionString = builder.Configuration.GetConnectionString("Redis");
+if (cacheOptions.Enabled && !string.IsNullOrWhiteSpace(redisConnectionString))
+{
+    builder.Services.AddStackExchangeRedisCache(options =>
+        options.Configuration = redisConnectionString);
+}
+builder.Services.AddHybridCache(options =>
+{
+    options.MaximumKeyLength = 512;
+    options.MaximumPayloadBytes = cacheOptions.MaximumPayloadKilobytes * 1024;
+});
+builder.Services.AddSingleton<IAppCache, HybridAppCache>();
+
 builder.Services
     .AddIdentityCore<ApplicationUser>(options =>
     {
@@ -320,6 +355,7 @@ app.MapGet("/health/live", () => Results.Ok(new { Status = "healthy" }))
     .AllowAnonymous();
 app.MapGet("/health", CheckDatabaseHealthAsync).AllowAnonymous();
 app.MapGet("/health/ready", CheckDatabaseHealthAsync).AllowAnonymous();
+app.MapGet("/health/cache", CheckCacheHealthAsync).AllowAnonymous();
 app.MapFallback(async context =>
 {
     if (context.Request.Path.StartsWithSegments("/api") ||
@@ -383,4 +419,27 @@ static async Task<IResult> CheckDatabaseHealthAsync(
     }
 }
 
+static async Task<IResult> CheckCacheHealthAsync(
+    IServiceProvider services,
+    CancellationToken cancellationToken)
+{
+    var distributedCache = services.GetService<IDistributedCache>();
+    if (distributedCache is null)
+        return Results.Ok(new { Status = "disabled", Backend = "memory" });
+
+    try
+    {
+        await distributedCache.GetAsync(
+            "jiaowu:health:probe",
+            cancellationToken);
+        return Results.Ok(new { Status = "healthy", Backend = "redis" });
+    }
+    catch
+    {
+        return Results.Json(
+            new { Status = "unhealthy", Backend = "redis" },
+            statusCode: StatusCodes.Status503ServiceUnavailable);
+    }
+}
+
 public partial class Program;