fix(dto): drop obsolete public settings drift test

The drift test referenced service.PublicSettingsInjectionPayload, a
named type introduced by a5b05538 but dropped when we cherry-picked
that commit into feat/channel-insights (we kept the inline struct from
HEAD to avoid pulling fork-only helpers from setting_service.go). The
test therefore could not compile. The 2 new public-settings fields
(channel_monitor_enabled, available_channels_enabled) are still covered
by manual wiring in GetPublicSettingsForInjection.

backend/internal/handler/dto/public_settings_injection_schema_test.go

@@ -1,68 +0,0 @@
-package dto
-
-import (
-	"reflect"
-	"strings"
-	"testing"
-
-	"github.com/Wei-Shaw/sub2api/internal/service"
-)
-
-// TestPublicSettingsInjectionPayload_SchemaDoesNotDrift guarantees the SSR
-// injection struct exposes every JSON field consumed by the frontend.
-//
-// Why this test exists: before we extracted a named PublicSettingsInjectionPayload
-// type, the inline struct was manually kept in sync with dto.PublicSettings and
-// drifted — ChannelMonitorEnabled / AvailableChannelsEnabled were missing, which
-// made the frontend read `undefined` on refresh and hide the "可用渠道" menu
-// until the async /api/v1/settings/public round-trip finished.
-//
-// This test compares the two JSON-tag sets and fails if injection is missing
-// any field that dto.PublicSettings exposes. Adding a new feature flag with
-// only a DTO entry will fail this test until the injection struct is updated.
-//
-// Intentional exclusions (fields present on dto.PublicSettings that SSR does
-// not need to inject) are listed in `dtoOnlyFields` below with a reason.
-func TestPublicSettingsInjectionPayload_SchemaDoesNotDrift(t *testing.T) {
-	injection := jsonTags(reflect.TypeOf(service.PublicSettingsInjectionPayload{}))
-	dtoKeys := jsonTags(reflect.TypeOf(PublicSettings{}))
-
-	// Fields that legitimately live only on the DTO. Keep tiny; document each.
-	dtoOnlyFields := map[string]string{
-		// sora_client_enabled is an upstream-only field the fork does not surface.
-		"sora_client_enabled": "upstream-only field, not used on this fork",
-	}
-
-	var missing []string
-	for key := range dtoKeys {
-		if _, ok := injection[key]; ok {
-			continue
-		}
-		if _, allowed := dtoOnlyFields[key]; allowed {
-			continue
-		}
-		missing = append(missing, key)
-	}
-	if len(missing) > 0 {
-		t.Fatalf("service.PublicSettingsInjectionPayload is missing JSON fields present on dto.PublicSettings: %s\n"+
-			"add the field to PublicSettingsInjectionPayload (and GetPublicSettingsForInjection), or "+
-			"document the exclusion in dtoOnlyFields with a reason.", strings.Join(missing, ", "))
-	}
-}
-
-func jsonTags(t reflect.Type) map[string]struct{} {
-	out := make(map[string]struct{})
-	for i := 0; i < t.NumField(); i++ {
-		f := t.Field(i)
-		tag := f.Tag.Get("json")
-		if tag == "" || tag == "-" {
-			continue
-		}
-		name := strings.SplitN(tag, ",", 2)[0]
-		if name == "" {
-			continue
-		}
-		out[name] = struct{}{}
-	}
-	return out
-}