refactor(affiliate): tighten DI and harden inviter code validation

- Drop SetAffiliateService setters and ProvideAuthService /
  ProvidePaymentService / ProvideUserHandler wrappers in favor of direct
  Wire constructor injection. AffiliateService has no back-edge to
  Auth/Payment/User, so the indirection was never required.
- Change RegisterWithVerification's variadic affiliateCode to a fixed
  parameter; adjust all call sites.
- Validate aff_code length and charset in BindInviterByCode before any
  DB lookup, eliminating timing-side-channel and useless DB roundtrips
  on malformed input.
- Make affiliate cache invalidation synchronous; surface Redis errors
  via the project logger instead of swallowing them in a detached
  goroutine.
- Add an integration test guarding cross-layer tx propagation in
  AccrueQuota and a unit test pinning the aff_code format rules.

backend/internal/server/middleware/admin_auth_test.go

@@ -20,7 +20,7 @@ func TestAdminAuthJWTValidatesTokenVersion(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 
 	cfg := &config.Config{JWT: config.JWTConfig{Secret: "test-secret", ExpireHour: 1}}
-	authService := service.NewAuthService(nil, nil, nil, nil, cfg, nil, nil, nil, nil, nil, nil)
+	authService := service.NewAuthService(nil, nil, nil, nil, cfg, nil, nil, nil, nil, nil, nil, nil)
 
 	admin := &service.User{
 		ID:           1,

backend/internal/server/middleware/jwt_auth_test.go

@@ -60,7 +60,7 @@ func newJWTTestEnv(users map[int64]*service.User) (*gin.Engine, *service.AuthSer
 	cfg.JWT.AccessTokenExpireMinutes = 60
 
 	userRepo := &stubJWTUserRepo{users: users}
-	authSvc := service.NewAuthService(nil, userRepo, nil, nil, cfg, nil, nil, nil, nil, nil, nil)
+	authSvc := service.NewAuthService(nil, userRepo, nil, nil, cfg, nil, nil, nil, nil, nil, nil, nil)
 	userSvc := service.NewUserService(userRepo, nil, nil, nil)
 	mw := NewJWTAuthMiddleware(authSvc, userSvc)
 
@@ -143,7 +143,7 @@ func TestJWTAuth_ValidToken_TouchesLastActive(t *testing.T) {
 	cfg.JWT.AccessTokenExpireMinutes = 60
 
 	userRepo := &stubJWTUserRepo{users: map[int64]*service.User{1: user}}
-	authSvc := service.NewAuthService(nil, userRepo, nil, nil, cfg, nil, nil, nil, nil, nil, nil)
+	authSvc := service.NewAuthService(nil, userRepo, nil, nil, cfg, nil, nil, nil, nil, nil, nil, nil)
 	userSvc := service.NewUserService(userRepo, nil, nil, nil)
 	toucher := &recordingActivityToucher{}