feat(core): bind request services and implement registered tasks

Wire plugin services through Bind/InjectFrom and AppContext so HTTP and
workers resolve dependencies after Apply. Register TaskHandler objects
with persisted results, and implement send_email_code, mail:send,
cleanup_inactive_users, and dispatch_bot_msg.

backend/plugins/domain/user/plugin.go

@@ -9,7 +9,6 @@ import (
 	"Wavelet/core/contracts"
 	"Wavelet/core/extpoints"
 	"Wavelet/pkg/ginutil"
-	"context"
 	"embed"
 	"reflect"
 
@@ -76,16 +75,13 @@ func (p *Plugin) Manifest() core.Manifest {
 
 // Apply registers user migrations, services, routes, tasks, schedules, and settings into the Context.
 func (p *Plugin) Apply(ctx *core.Context) error {
-	// 0. Bind DBService from Context
-	if db, err := core.Inject[contracts.DBService](ctx); err == nil && db != nil {
-		SetDBService(db)
-	} else {
-		core.When[contracts.DBService](ctx, func(db contracts.DBService) {
-			SetDBService(db)
-		})
-	}
+	core.Bind[contracts.DBService](ctx, SetDBService)
+	core.Bind[contracts.CacheService](ctx, SetCacheService)
+	core.Bind[contracts.TaskService](ctx, SetTaskService)
 	ctx.OnDispose(func() error {
 		SetDBService(nil)
+		SetCacheService(nil)
+		SetTaskService(nil)
 		return nil
 	})
 
@@ -101,11 +97,8 @@ func (p *Plugin) Apply(ctx *core.Context) error {
 		if mw, ok := authSvc.DisallowTokenAuthMiddleware().(gin.HandlerFunc); ok {
 			noTokenMW = mw
 		}
-	} else {
-		core.When[contracts.AuthService](ctx, func(svc contracts.AuthService) {
-			SetAuthService(svc)
-		})
 	}
+	core.Bind[contracts.AuthService](ctx, SetAuthService)
 	ctx.OnDispose(func() error {
 		SetAuthService(nil)
 		return nil
@@ -155,90 +148,12 @@ func (p *Plugin) Apply(ctx *core.Context) error {
 		}
 	}
 
-	const (
-		defaultUserTaskRetry = 3
-		paramTypeString      = "string"
-		paramNameEmail       = "email"
-	)
-
-	// 4. Register background tasks
-	ctx.Task().Register("user:send_email_code", func(_ context.Context, _ []byte) error {
-		return nil
-	},
-		extpoints.WithTaskType("send_email_code"),
-		extpoints.WithTaskName("发送邮箱验证码"),
-		extpoints.WithTaskDescription("异步发送用户注册与验证邮箱验证码"),
-		extpoints.WithTaskCategory("user"),
-		extpoints.WithTaskRetry(defaultUserTaskRetry),
-		extpoints.WithTaskQueue("default"),
-		extpoints.WithTaskRetryable(true),
-		extpoints.WithTaskParams(
-			contracts.TaskParamDTO{
-				Name:        paramNameEmail,
-				Label:       "目标邮箱",
-				Type:        paramTypeString,
-				Required:    true,
-				Placeholder: "user@example.com",
-				Description: "接收验证码的目标邮箱",
-			},
-			contracts.TaskParamDTO{
-				Name:        "code",
-				Label:       "验证码",
-				Type:        paramTypeString,
-				Required:    true,
-				Placeholder: "123456",
-				Description: "6 位数字验证码",
-			},
-		),
-	)
-
-	ctx.Task().Register("mail:send", func(_ context.Context, _ []byte) error {
-		return nil
-	},
-		extpoints.WithTaskType("send_email"),
-		extpoints.WithTaskName("发送邮件"),
-		extpoints.WithTaskDescription("异步发送系统邮件"),
-		extpoints.WithTaskCategory("mail"),
-		extpoints.WithTaskRetry(defaultUserTaskRetry),
-		extpoints.WithTaskQueue("default"),
-		extpoints.WithTaskRetryable(true),
-		extpoints.WithTaskParams(
-			contracts.TaskParamDTO{
-				Name:        "to",
-				Label:       "接收邮箱 (To)",
-				Type:        paramTypeString,
-				Required:    true,
-				Placeholder: "receiver@example.com",
-				Description: "接收邮件的目标邮箱地址",
-			},
-			contracts.TaskParamDTO{
-				Name:        "subject",
-				Label:       "邮件主题 (Subject)",
-				Type:        paramTypeString,
-				Required:    true,
-				Placeholder: "请输入邮件主题",
-				Description: "发送邮件的主题标题",
-			},
-			contracts.TaskParamDTO{
-				Name:        "body",
-				Label:       "邮件内容 (Body)",
-				Type:        "text",
-				Required:    true,
-				Placeholder: "请输入邮件内容（支持 HTML格式）",
-				Description: "发送邮件的内容主体",
-			},
-		),
-	)
-
-	ctx.Task().Register("user:cleanup_inactive", func(_ context.Context, _ []byte) error {
-		return nil
-	},
-		extpoints.WithTaskType("cleanup_inactive_users"),
-		extpoints.WithTaskName("清理未激活用户"),
-		extpoints.WithTaskDescription("清理长期未激活的注册用户与临时凭据"),
-		extpoints.WithTaskCategory("user"),
-		extpoints.WithTaskQueue("default"),
-	)
+	ctx.Task().Register(TaskSendEmailCode, &SendEmailCodeHandler{},
+		extpoints.WithTaskMeta(SendEmailCodeMeta), extpoints.WithTaskRetry(defaultUserTaskRetry))
+	ctx.Task().Register(TaskSendMail, &SendMailHandler{},
+		extpoints.WithTaskMeta(SendMailMeta), extpoints.WithTaskRetry(defaultUserTaskRetry))
+	ctx.Task().Register(TaskCleanupInactive, &CleanupInactiveHandler{},
+		extpoints.WithTaskMeta(CleanupInactiveMeta))
 
 	// 5. Register Settings Schemas
 	ctx.Settings().Register(extpoints.SettingSchema{