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/migrations/024_add_gemini_tier_id.sql

@@ -1,30 +1,30 @@
--- +goose Up
--- +goose StatementBegin
--- 为 Gemini Code Assist OAuth 账号添加默认 tier_id
--- 包括显式标记为 code_assist 的账号，以及 legacy 账号（oauth_type 为空但 project_id 存在）
-UPDATE accounts
-SET credentials = jsonb_set(
-    credentials,
-    '{tier_id}',
-    '"LEGACY"',
-    true
-)
-WHERE platform = 'gemini'
-  AND type = 'oauth'
-  AND jsonb_typeof(credentials) = 'object'
-  AND credentials->>'tier_id' IS NULL
-  AND (
-    credentials->>'oauth_type' = 'code_assist'
-    OR (credentials->>'oauth_type' IS NULL AND credentials->>'project_id' IS NOT NULL)
-  );
--- +goose StatementEnd
-
--- +goose Down
--- +goose StatementBegin
--- 回滚：删除 tier_id 字段
-UPDATE accounts
-SET credentials = credentials - 'tier_id'
-WHERE platform = 'gemini'
-  AND type = 'oauth'
-  AND credentials ? 'tier_id';
--- +goose StatementEnd
+-- +goose Up
+-- +goose StatementBegin
+-- 为 Gemini Code Assist OAuth 账号添加默认 tier_id
+-- 包括显式标记为 code_assist 的账号，以及 legacy 账号（oauth_type 为空但 project_id 存在）
+UPDATE accounts
+SET credentials = jsonb_set(
+    credentials,
+    '{tier_id}',
+    '"LEGACY"',
+    true
+)
+WHERE platform = 'gemini'
+  AND type = 'oauth'
+  AND jsonb_typeof(credentials) = 'object'
+  AND credentials->>'tier_id' IS NULL
+  AND (
+    credentials->>'oauth_type' = 'code_assist'
+    OR (credentials->>'oauth_type' IS NULL AND credentials->>'project_id' IS NOT NULL)
+  );
+-- +goose StatementEnd
+
+-- +goose Down
+-- +goose StatementBegin
+-- 回滚：删除 tier_id 字段
+UPDATE accounts
+SET credentials = credentials - 'tier_id'
+WHERE platform = 'gemini'
+  AND type = 'oauth'
+  AND credentials ? 'tier_id';
+-- +goose StatementEnd