feat: 品牌重命名 Sub2API -> TianShuAPI

- 前端: 所有界面显示、i18n 文本、组件中的品牌名称
- 后端: 服务层、设置默认值、邮件模板、安装向导
- 数据库: 迁移脚本注释
- 保持功能完全一致，仅更改品牌名称

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/internal/service/billing_cache_service_test.go

@@ -1,75 +1,75 @@
-package service
-
-import (
-	"context"
-	"errors"
-	"sync/atomic"
-	"testing"
-	"time"
-
-	"github.com/Wei-Shaw/sub2api/internal/config"
-	"github.com/stretchr/testify/require"
-)
-
-type billingCacheWorkerStub struct {
-	balanceUpdates      int64
-	subscriptionUpdates int64
-}
-
-func (b *billingCacheWorkerStub) GetUserBalance(ctx context.Context, userID int64) (float64, error) {
-	return 0, errors.New("not implemented")
-}
-
-func (b *billingCacheWorkerStub) SetUserBalance(ctx context.Context, userID int64, balance float64) error {
-	atomic.AddInt64(&b.balanceUpdates, 1)
-	return nil
-}
-
-func (b *billingCacheWorkerStub) DeductUserBalance(ctx context.Context, userID int64, amount float64) error {
-	atomic.AddInt64(&b.balanceUpdates, 1)
-	return nil
-}
-
-func (b *billingCacheWorkerStub) InvalidateUserBalance(ctx context.Context, userID int64) error {
-	return nil
-}
-
-func (b *billingCacheWorkerStub) GetSubscriptionCache(ctx context.Context, userID, groupID int64) (*SubscriptionCacheData, error) {
-	return nil, errors.New("not implemented")
-}
-
-func (b *billingCacheWorkerStub) SetSubscriptionCache(ctx context.Context, userID, groupID int64, data *SubscriptionCacheData) error {
-	atomic.AddInt64(&b.subscriptionUpdates, 1)
-	return nil
-}
-
-func (b *billingCacheWorkerStub) UpdateSubscriptionUsage(ctx context.Context, userID, groupID int64, cost float64) error {
-	atomic.AddInt64(&b.subscriptionUpdates, 1)
-	return nil
-}
-
-func (b *billingCacheWorkerStub) InvalidateSubscriptionCache(ctx context.Context, userID, groupID int64) error {
-	return nil
-}
-
-func TestBillingCacheServiceQueueHighLoad(t *testing.T) {
-	cache := &billingCacheWorkerStub{}
-	svc := NewBillingCacheService(cache, nil, nil, &config.Config{})
-	t.Cleanup(svc.Stop)
-
-	start := time.Now()
-	for i := 0; i < cacheWriteBufferSize*2; i++ {
-		svc.QueueDeductBalance(1, 1)
-	}
-	require.Less(t, time.Since(start), 2*time.Second)
-
-	svc.QueueUpdateSubscriptionUsage(1, 2, 1.5)
-
-	require.Eventually(t, func() bool {
-		return atomic.LoadInt64(&cache.balanceUpdates) > 0
-	}, 2*time.Second, 10*time.Millisecond)
-
-	require.Eventually(t, func() bool {
-		return atomic.LoadInt64(&cache.subscriptionUpdates) > 0
-	}, 2*time.Second, 10*time.Millisecond)
-}
+package service
+
+import (
+	"context"
+	"errors"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/stretchr/testify/require"
+)
+
+type billingCacheWorkerStub struct {
+	balanceUpdates      int64
+	subscriptionUpdates int64
+}
+
+func (b *billingCacheWorkerStub) GetUserBalance(ctx context.Context, userID int64) (float64, error) {
+	return 0, errors.New("not implemented")
+}
+
+func (b *billingCacheWorkerStub) SetUserBalance(ctx context.Context, userID int64, balance float64) error {
+	atomic.AddInt64(&b.balanceUpdates, 1)
+	return nil
+}
+
+func (b *billingCacheWorkerStub) DeductUserBalance(ctx context.Context, userID int64, amount float64) error {
+	atomic.AddInt64(&b.balanceUpdates, 1)
+	return nil
+}
+
+func (b *billingCacheWorkerStub) InvalidateUserBalance(ctx context.Context, userID int64) error {
+	return nil
+}
+
+func (b *billingCacheWorkerStub) GetSubscriptionCache(ctx context.Context, userID, groupID int64) (*SubscriptionCacheData, error) {
+	return nil, errors.New("not implemented")
+}
+
+func (b *billingCacheWorkerStub) SetSubscriptionCache(ctx context.Context, userID, groupID int64, data *SubscriptionCacheData) error {
+	atomic.AddInt64(&b.subscriptionUpdates, 1)
+	return nil
+}
+
+func (b *billingCacheWorkerStub) UpdateSubscriptionUsage(ctx context.Context, userID, groupID int64, cost float64) error {
+	atomic.AddInt64(&b.subscriptionUpdates, 1)
+	return nil
+}
+
+func (b *billingCacheWorkerStub) InvalidateSubscriptionCache(ctx context.Context, userID, groupID int64) error {
+	return nil
+}
+
+func TestBillingCacheServiceQueueHighLoad(t *testing.T) {
+	cache := &billingCacheWorkerStub{}
+	svc := NewBillingCacheService(cache, nil, nil, &config.Config{})
+	t.Cleanup(svc.Stop)
+
+	start := time.Now()
+	for i := 0; i < cacheWriteBufferSize*2; i++ {
+		svc.QueueDeductBalance(1, 1)
+	}
+	require.Less(t, time.Since(start), 2*time.Second)
+
+	svc.QueueUpdateSubscriptionUsage(1, 2, 1.5)
+
+	require.Eventually(t, func() bool {
+		return atomic.LoadInt64(&cache.balanceUpdates) > 0
+	}, 2*time.Second, 10*time.Millisecond)
+
+	require.Eventually(t, func() bool {
+		return atomic.LoadInt64(&cache.subscriptionUpdates) > 0
+	}, 2*time.Second, 10*time.Millisecond)
+}