refactor: 彻底移除 Sora 视频生成模块（全栈清理）

## 后端变更
- 删除 21 个 sora_*.go 服务文件（service/handler/repository/routes）
- 删除 Sora 相关 migration 文件（046/047/063/090）
- 清理 config 中的 sora_* 配置项和平台常量
- 清理 wire 依赖注入中的 Sora 组件
- 修复 wire_gen.go 语法错误（缺少逗号和闭合括号）
- 移除 go.mod 中的 go-sora2api 依赖
- 更新 ent schema usage_log.go 注释

## 前端变更
- 删除 SoraView、SoraAdminView 及 8 个 Sora 子组件
- 删除 sora API 层和路由配置
- 清理 UserEditModal 中的 Sora 存储配额 UI
- 清理 types/index.ts 中 Sora 相关类型定义
- 清理 stores/app.ts 默认配置
- 清理 i18n 翻译文件 en.ts/zh.ts (~110 行)
- 更新相关测试文件

## 文档更新
- README.md / README_CN.md / README_JA.md: 移除 Sora 状态说明和配置段落
- PROJECT_DIFF.md: 移除 Sora 相关差异描述

## 验证结果
- ✅ Go 编译通过 (go build ./...)
- ✅ TypeScript 类型检查通过 (vue-tsc --noEmit)
- ✅ 后端测试全通过 (0 failures)
- ✅ 前端测试全通过 (59 files, 329 tests, 0 failures)
- ✅ 前端生产构建成功 (23.81s)

backend/migrations/045_add_accounts_extra_index.sql

@@ -1,6 +1,6 @@
 -- Migration: 045_add_accounts_extra_index
 -- 为 accounts.extra 字段添加 GIN 索引，优化 FindByExtraField 查询性能
--- 用于支持通过 extra 字段中的 linked_openai_account_id 快速查找关联的 Sora 账号
+-- 用于支持通过 extra 字段中的 linked_openai_account_id 快速查找关联的账号
 
 CREATE INDEX IF NOT EXISTS idx_accounts_extra_gin
 ON accounts USING GIN (extra);
@@ -8,6 +8,5 @@ ON accounts USING GIN (extra);
 -- 查询示例（使用 @> 操作符）
 -- EXPLAIN ANALYZE
 -- SELECT * FROM accounts
--- WHERE platform = 'sora'
---   AND extra @> '{"linked_openai_account_id": 123}'::jsonb
+-- WHERE extra @> '{"linked_openai_account_id": 123}'::jsonb
 --   AND deleted_at IS NULL;

backend/migrations/046_add_sora_accounts.sql

@@ -1,24 +0,0 @@
--- Migration: 046_add_sora_accounts
--- 新增 sora_accounts 扩展表，存储 Sora 账号的 OAuth 凭证
--- 与 accounts 主表形成双表结构：
---   - accounts: 统一账号管理和调度
---   - sora_accounts: Sora gateway 快速读取和资格校验
---
--- 设计说明：
---   - account_id 为主键，外键关联 accounts.id
---   - ON DELETE CASCADE 确保删除账号时自动清理扩展表
---   - access_token/refresh_token 与 accounts.credentials 保持同步
-
-CREATE TABLE IF NOT EXISTS sora_accounts (
-    account_id BIGINT PRIMARY KEY,
-    access_token TEXT NOT NULL,
-    refresh_token TEXT NOT NULL,
-    session_token TEXT,
-    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
-    CONSTRAINT fk_sora_accounts_account_id
-        FOREIGN KEY (account_id) REFERENCES accounts(id)
-        ON DELETE CASCADE
-);
-
--- 索引说明：主键已自动创建唯一索引，无需额外创建 idx_sora_accounts_account_id

backend/migrations/047_add_sora_pricing_and_media_type.sql

@@ -1,11 +0,0 @@
--- Migration: 047_add_sora_pricing_and_media_type
--- 新增 Sora 按次计费字段与 usage_logs.media_type
-
-ALTER TABLE groups
-	ADD COLUMN IF NOT EXISTS sora_image_price_360 decimal(20,8),
-	ADD COLUMN IF NOT EXISTS sora_image_price_540 decimal(20,8),
-	ADD COLUMN IF NOT EXISTS sora_video_price_per_request decimal(20,8),
-	ADD COLUMN IF NOT EXISTS sora_video_price_per_request_hd decimal(20,8);
-
-ALTER TABLE usage_logs
-	ADD COLUMN IF NOT EXISTS media_type VARCHAR(16);

backend/migrations/063_add_sora_client_tables.sql

@@ -1,56 +0,0 @@
--- Migration: 063_add_sora_client_tables
--- Sora 客户端功能所需的数据库变更：
---   1. 新增 sora_generations 表：记录 Sora 客户端 UI 的生成历史
---   2. users 表新增存储配额字段
---   3. groups 表新增存储配额字段
-
--- ============================================================
--- 1. sora_generations 表（生成记录）
--- ============================================================
-CREATE TABLE IF NOT EXISTS sora_generations (
-    id               BIGSERIAL PRIMARY KEY,
-    user_id          BIGINT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
-    api_key_id       BIGINT,
-
-    -- 生成参数
-    model            VARCHAR(64) NOT NULL,
-    prompt           TEXT NOT NULL DEFAULT '',
-    media_type       VARCHAR(16) NOT NULL DEFAULT 'video',    -- video / image
-
-    -- 结果
-    status           VARCHAR(16) NOT NULL DEFAULT 'pending',  -- pending / generating / completed / failed / cancelled
-    media_url        TEXT NOT NULL DEFAULT '',
-    media_urls       JSONB,                                   -- 多图时的 URL 数组
-    file_size_bytes  BIGINT NOT NULL DEFAULT 0,
-    storage_type     VARCHAR(16) NOT NULL DEFAULT 'none',     -- s3 / local / upstream / none
-    s3_object_keys   JSONB,                                   -- S3 object key 数组
-
-    -- 上游信息
-    upstream_task_id VARCHAR(128) NOT NULL DEFAULT '',
-    error_message    TEXT NOT NULL DEFAULT '',
-
-    -- 时间
-    created_at       TIMESTAMPTZ NOT NULL DEFAULT NOW(),
-    completed_at     TIMESTAMPTZ
-);
-
--- 按用户+时间查询（作品库列表、历史记录）
-CREATE INDEX IF NOT EXISTS idx_sora_gen_user_created
-    ON sora_generations(user_id, created_at DESC);
-
--- 按用户+状态查询（恢复进行中任务）
-CREATE INDEX IF NOT EXISTS idx_sora_gen_user_status
-    ON sora_generations(user_id, status);
-
--- ============================================================
--- 2. users 表新增 Sora 存储配额字段
--- ============================================================
-ALTER TABLE users
-    ADD COLUMN IF NOT EXISTS sora_storage_quota_bytes BIGINT NOT NULL DEFAULT 0,
-    ADD COLUMN IF NOT EXISTS sora_storage_used_bytes  BIGINT NOT NULL DEFAULT 0;
-
--- ============================================================
--- 3. groups 表新增 Sora 存储配额字段
--- ============================================================
-ALTER TABLE groups
-    ADD COLUMN IF NOT EXISTS sora_storage_quota_bytes BIGINT NOT NULL DEFAULT 0;

backend/migrations/090_drop_sora.sql

@@ -1,34 +0,0 @@
--- Migration: 090_drop_sora
--- Remove all Sora-related database objects.
--- Drops tables: sora_tasks, sora_generations, sora_accounts
--- Drops columns from: groups, users, usage_logs
-
--- ============================================================
--- 1. Drop Sora tables
--- ============================================================
-DROP TABLE IF EXISTS sora_tasks;
-DROP TABLE IF EXISTS sora_generations;
-DROP TABLE IF EXISTS sora_accounts;
-
--- ============================================================
--- 2. Drop Sora columns from groups table
--- ============================================================
-ALTER TABLE groups
-    DROP COLUMN IF EXISTS sora_image_price_360,
-    DROP COLUMN IF EXISTS sora_image_price_540,
-    DROP COLUMN IF EXISTS sora_video_price_per_request,
-    DROP COLUMN IF EXISTS sora_video_price_per_request_hd,
-    DROP COLUMN IF EXISTS sora_storage_quota_bytes;
-
--- ============================================================
--- 3. Drop Sora columns from users table
--- ============================================================
-ALTER TABLE users
-    DROP COLUMN IF EXISTS sora_storage_quota_bytes,
-    DROP COLUMN IF EXISTS sora_storage_used_bytes;
-
--- ============================================================
--- 4. Drop Sora column from usage_logs table
--- ============================================================
-ALTER TABLE usage_logs
-    DROP COLUMN IF EXISTS media_type;