feat: 上架版本号按分支拆分，master / develop 各自独立

原来 master 与 develop 共用一条 release 轨，版本号和构建号绑在一起。
现改为每个上架分支各有一条轨道（轨道名即分支名），自测分支仍共用 feature 轨。

- 轨道记录新增 kind（release/feature），branch_track 存轨道名
- 旧的共用 release 轨及更早的单轨结构，加载时自动按上架分支拆开，
  已用构建号原样复制，拆分后各分支从原来的号继续递增
- 构建号递增时跨上架轨取同一 App_Ver 的最大值 +1：App Store 的构建号
  唯一性按 MARKETING_VERSION 全局判定，避免两分支同版本号时重号被拒
- 分支管理页轨道选择改为「上架（本分支独立版本号）/ 自测（共用）」，
  打包设置页按上架分支分块填写版本号

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BJaZ913U5GVdTkYHiRpvDU

CLAUDE.md

@@ -26,7 +26,7 @@ FastAPI + Vue 3 iOS app auto-packaging service. Supports Ad_Hoc and App_Store bu
 - `backend/config.py` — loads .env, defines all config constants
 - `frontend/src/views/` — BuildView, HistoryView, ConfigView
 - `config.json` — runtime config (apps, schemes, servers, upload, branches, versions) managed via web UI
-- Versions are per-track: `release` (master/develop, build number auto-increments on App_Store) and `feature` (self-test, never increments); each branch's track lives in `config["branch_track"]`
+- Versions are per-track: each release branch (master, develop, …) has its own track named after the branch (build number auto-increments on App_Store), and all self-test branches share the `feature` track (never increments); each branch's track name lives in `config["branch_track"]`, track records in `config["versions"]["tracks"]` carry `kind` (release/feature)
 
 ## Conventions