feat: 支持按 Tag 打包，分支管理可添加 Tag

- 分支管理新增「分支 / Tag」类型选择，Tag 存于 config["tags"]，与分支不可重名
- 每个 Tag 与分支一样拥有同名独立版本轨道，默认上架轨
- 打包页按「分支」「Tag」分组选择；任务新增 ref_type 字段记录引用类型
- Tag 打包时 fetch --tags --force 后以游离 HEAD 检出 refs/tags/<tag>
- 历史记录与下载页按类型显示「分支」或「Tag」

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/services/build_service.py

@@ -291,8 +291,8 @@ def _db_update(db, task, **fields):
     db.commit()
 
 
-async def update_source(task_id: str, source_dir: Path, branch: str):
-    """将共享源码工作目录强制同步到指定远程分支。"""
+async def update_source(task_id: str, source_dir: Path, branch: str, ref_type: str = "branch"):
+    """将共享源码工作目录强制同步到指定远程分支或 Tag（ref_type="tag" 时 branch 为 Tag 名）。"""
     remote_url = get_git_remote_url(with_credentials=True)
     remote_url_masked = mask_git_remote_url(remote_url)
     git_env = _git_env()
@@ -321,7 +321,8 @@ async def update_source(task_id: str, source_dir: Path, branch: str):
     if not cloned and not (source_dir / ".git").exists():
         raise Exception(f"共享源码目录不是 Git 仓库: {source_dir}")
 
-    await log_streamer.emit(task_id, f"同步共享源码到分支: {branch}")
+    is_tag = ref_type == "tag"
+    await log_streamer.emit(task_id, f"同步共享源码到{'Tag' if is_tag else '分支'}: {branch}")
 
     if remote_url:
         process = await asyncio.create_subprocess_exec(
@@ -333,12 +334,22 @@ async def update_source(task_id: str, source_dir: Path, branch: str):
         if process.returncode != 0:
             raise Exception("git remote set-url 失败")
 
-    commands = [
-        (("git", "fetch", "origin"), "git fetch 失败"),
-        (("git", "checkout", "-B", branch, f"origin/{branch}"), f"git checkout {branch} 失败"),
-        (("git", "reset", "--hard", f"origin/{branch}"), f"git reset {branch} 失败"),
-        (("git", "clean", "-ffdx"), "git clean 失败"),
-    ]
+    if is_tag:
+        # Tag 检出为游离 HEAD；--force 让远端被移动过的 Tag 覆盖本地旧 Tag
+        tag_ref = f"refs/tags/{branch}"
+        commands = [
+            (("git", "fetch", "origin", "--tags", "--force"), "git fetch 失败"),
+            (("git", "checkout", "--detach", tag_ref), f"git checkout Tag {branch} 失败"),
+            (("git", "reset", "--hard", tag_ref), f"git reset Tag {branch} 失败"),
+            (("git", "clean", "-ffdx"), "git clean 失败"),
+        ]
+    else:
+        commands = [
+            (("git", "fetch", "origin"), "git fetch 失败"),
+            (("git", "checkout", "-B", branch, f"origin/{branch}"), f"git checkout {branch} 失败"),
+            (("git", "reset", "--hard", f"origin/{branch}"), f"git reset {branch} 失败"),
+            (("git", "clean", "-ffdx"), "git clean 失败"),
+        ]
     for command, error_message in commands:
         process = await asyncio.create_subprocess_exec(
             *_GIT_NO_CREDENTIAL_HELPER, *command[1:], env=git_env,
@@ -375,7 +386,7 @@ async def prepare_source_snapshot(task_id: str, task) -> tuple[Path, str]:
         source_dir = get_source_dir(task.branch)
         if not source_dir.exists():
             raise Exception(
-                f"分支源码目录不存在: {source_dir}，请先在 GIT_SOURCE_BASE 下准备分支代码，或配置 GIT_REMOTE_URL"
+                f"分支源码目录不存在: {source_dir}，请先在 GIT_SOURCE_BASE 下准备分支（或 Tag）代码，或配置 GIT_REMOTE_URL"
             )
         await log_streamer.emit(task_id, f"使用分支源码: {source_dir}")
         return await copy_source_code(task_id, task, source_dir), ""
@@ -384,7 +395,8 @@ async def prepare_source_snapshot(task_id: str, task) -> tuple[Path, str]:
     await log_streamer.emit(task_id, "等待共享源码准备队列...")
     async with source_prepare_lock:
         await log_streamer.emit(task_id, "开始准备共享源码快照")
-        await update_source(task_id, source_dir, task.branch)
+        ref_type = "tag" if task.ref_type == "tag" else "branch"
+        await update_source(task_id, source_dir, task.branch, ref_type)
         commit = await get_source_commit(source_dir)
         await log_streamer.emit(task_id, f"源码版本: {task.branch} @ {commit}")
         build_dir = await copy_source_code(task_id, task, source_dir)
@@ -433,6 +445,7 @@ async def run_build_task(task_id: str):
                 await asyncio.to_thread(_db_update, db, task, current_step="config")
                 config_data = await generate_config(task_id, task, build_dir)
                 config_data["SOURCE_BRANCH"] = task.branch
+                config_data["SOURCE_REF_TYPE"] = "tag" if task.ref_type == "tag" else "branch"
                 config_data["SOURCE_COMMIT"] = source_commit
                 await asyncio.to_thread(_db_update, db, task,
                                         config_json=json.dumps(config_data, ensure_ascii=False))