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/repository/gateway_cache.go

@@ -1,34 +1,34 @@
-package repository
-
-import (
-	"context"
-	"time"
-
-	"github.com/Wei-Shaw/sub2api/internal/service"
-	"github.com/redis/go-redis/v9"
-)
-
-const stickySessionPrefix = "sticky_session:"
-
-type gatewayCache struct {
-	rdb *redis.Client
-}
-
-func NewGatewayCache(rdb *redis.Client) service.GatewayCache {
-	return &gatewayCache{rdb: rdb}
-}
-
-func (c *gatewayCache) GetSessionAccountID(ctx context.Context, sessionHash string) (int64, error) {
-	key := stickySessionPrefix + sessionHash
-	return c.rdb.Get(ctx, key).Int64()
-}
-
-func (c *gatewayCache) SetSessionAccountID(ctx context.Context, sessionHash string, accountID int64, ttl time.Duration) error {
-	key := stickySessionPrefix + sessionHash
-	return c.rdb.Set(ctx, key, accountID, ttl).Err()
-}
-
-func (c *gatewayCache) RefreshSessionTTL(ctx context.Context, sessionHash string, ttl time.Duration) error {
-	key := stickySessionPrefix + sessionHash
-	return c.rdb.Expire(ctx, key, ttl).Err()
-}
+package repository
+
+import (
+	"context"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/service"
+	"github.com/redis/go-redis/v9"
+)
+
+const stickySessionPrefix = "sticky_session:"
+
+type gatewayCache struct {
+	rdb *redis.Client
+}
+
+func NewGatewayCache(rdb *redis.Client) service.GatewayCache {
+	return &gatewayCache{rdb: rdb}
+}
+
+func (c *gatewayCache) GetSessionAccountID(ctx context.Context, sessionHash string) (int64, error) {
+	key := stickySessionPrefix + sessionHash
+	return c.rdb.Get(ctx, key).Int64()
+}
+
+func (c *gatewayCache) SetSessionAccountID(ctx context.Context, sessionHash string, accountID int64, ttl time.Duration) error {
+	key := stickySessionPrefix + sessionHash
+	return c.rdb.Set(ctx, key, accountID, ttl).Err()
+}
+
+func (c *gatewayCache) RefreshSessionTTL(ctx context.Context, sessionHash string, ttl time.Duration) error {
+	key := stickySessionPrefix + sessionHash
+	return c.rdb.Expire(ctx, key, ttl).Err()
+}