feat: 新增文件库功能，支持局域网文件浏览与媒体播放

后端：
- 新增 ManagedLibraryRoot / ManagedFileRecord 数据模型及 SQLite 迁移
- 新增文件库服务、端点服务及定时扫描后台任务
- 新增 REST API: drives、directories、roots CRUD、files 分页搜索、文本预览
- 新增文件流端点支持视频/音频流式传输
- 数据库切换为 SQLite，Kestrel 绑定 0.0.0.0 支持局域网访问

前端：
- 管理端：磁盘浏览、目录选择、根目录添加/启用/删除/扫描
- 客户端：根目录选择、文件搜索/筛选/分页、音视频播放、文本预览
- 全新响应式 UI（桌面+移动端），CSS 变量设计系统
- HTTP 客户端支持 Vite 开发代理与生产同源自动切换
- 移除 HTTPS 强制重定向以提升移动端视频流兼容性

Avalonia-Services/Endpoints/AppEndpoints.cs

@@ -3,6 +3,7 @@ using Avalonia_EFCore.Database;
 using Avalonia_EFCore.Models;
 using Avalonia_Services.Core;
 using Avalonia_Services.Services;
+using Avalonia_Services.Services.FileLibrary;
 using Microsoft.EntityFrameworkCore;
 
 namespace Avalonia_Services.Endpoints
@@ -47,6 +48,46 @@ namespace Avalonia_Services.Endpoints
                 endpoints.MapPost("api/processData", ProcessDataAsync)
                     .WithName("ProcessData");
 
+                endpoints.MapGet<IFileLibraryEndpointService>("api/library/drives", (service, ctx) => service.GetDrivesAsync(ctx))
+                    .WithOpenApi("FileLibrary", "查询服务器磁盘。")
+                    .WithName("GetLibraryDrives");
+
+                endpoints.MapGet<IFileLibraryEndpointService>("api/library/directories", (service, ctx) => service.GetDirectoriesAsync(ctx))
+                    .WithOpenApi("FileLibrary", "查询服务器目录。")
+                    .WithName("GetLibraryDirectories");
+
+                endpoints.MapGet<IFileLibraryEndpointService>("api/library/roots", (service, ctx) => service.GetRootsAsync(ctx))
+                    .WithOpenApi("FileLibrary", "查询文件库目录。")
+                    .WithName("GetLibraryRoots");
+
+                endpoints.MapPost<IFileLibraryEndpointService>("api/library/roots", (service, ctx) => service.AddRootAsync(ctx))
+                    .WithOpenApi("FileLibrary", "添加文件库目录。")
+                    .WithName("AddLibraryRoot");
+
+                endpoints.MapPost<IFileLibraryEndpointService>("api/library/roots/enabled", (service, ctx) => service.SetRootEnabledAsync(ctx))
+                    .WithOpenApi("FileLibrary", "启用或禁用文件库目录。")
+                    .WithName("SetLibraryRootEnabled");
+
+                endpoints.MapPost<IFileLibraryEndpointService>("api/library/roots/delete", (service, ctx) => service.DeleteRootAsync(ctx))
+                    .WithOpenApi("FileLibrary", "删除文件库目录。")
+                    .WithName("DeleteLibraryRoot");
+
+                endpoints.MapPost<IFileLibraryEndpointService>("api/library/roots/scan", (service, ctx) => service.ScanRootAsync(ctx))
+                    .WithOpenApi("FileLibrary", "立即扫描文件库目录。")
+                    .WithName("ScanLibraryRoot");
+
+                endpoints.MapGet<IFileLibraryEndpointService>("api/files", (service, ctx) => service.SearchFilesAsync(ctx))
+                    .WithOpenApi("FileLibrary", "分页查询已扫描文件。")
+                    .WithName("SearchFiles");
+
+                endpoints.MapGet<IFileLibraryEndpointService>("api/files/detail", (service, ctx) => service.GetFileAsync(ctx))
+                    .WithOpenApi("FileLibrary", "查询文件详情。")
+                    .WithName("GetFileDetail");
+
+                endpoints.MapGet<IFileLibraryEndpointService>("api/files/text", (service, ctx) => service.GetTextPreviewAsync(ctx))
+                    .WithOpenApi("FileLibrary", "预览文本文件。")
+                    .WithName("GetTextPreview");
+
                 // ---- 需要鉴权的端点示例 ----
                 // endpoints.MapGet("api/admin/dashboard", AdminDashboardAsync)
                 //     .WithName("AdminDashboard")