fix(alignment): /tree accept and apply map_id filter for KPI selection

GET /api/cma/alignment/tree ignored the map_id query param (FastAPI silently dropped it) so the board always rendered the full active-KPI set of the account. Add map_id: Optional[int] = Query(None) and filter KPIDefinition.map_id when provided; no param keeps the previous behaviour. Entity scoping unchanged (entity_id from token) - cross-account map_id yields an empty tree, no other-account KPI is returned. Only the KPI selection set is filtered; vertical/horizontal/bsc_chain builders untouched.

backend/app/api/alignment.py

@@ -129,6 +129,7 @@ def set_alignment_config(
 @router.get("/tree")
 def get_alignment_tree(
     kpi_id: Optional[int] = Query(None),
+    map_id: Optional[int] = Query(None),
     entity_id: int = Depends(get_entity_id),
     db: Session = Depends(get_db),
     user = Depends(require_auth),
@@ -143,6 +144,13 @@ def get_alignment_tree(
     只取 entity_id 归属本账套的 KPI（entity_id 来自会话 token 绑定，写法对齐
     growth-quality / predict.accuracy）。三种模式共用本列表 → 三模式同时隔离。
     跨实体显式传参（?entity_id=<他人账套>）由 get_entity_id 返回 403。
+
+    地图筛选（2026-10-01 project-20261001-align-tree-map-filter-fullstack）：
+    `map_id` 参与**KPI 选择集**过滤——给定 map_id 时只保留
+    `KPIDefinition.map_id == map_id` 的本账套 active KPI；不传时维持改前行为（全量）。
+    跨账套 map_id：KPI 选择集本身已按 entity_id 隔离（且关联写入端点
+    `PUT /kpis/{id}/associate-map` 亦强制 KPI↔地图同账套）⇒ 返回空树，不泄漏他账套 KPI。
+    过滤只作用于 KPI 选择集，三种模式的构建函数（vertical/horizontal/bsc_chain）不变。
     """
     # 获取当前账套的对齐模式（B3(a) 拆账套 2026-09-22：只读 alignment_config.<entity_id>）
     config_perm = _get_alignment_perm(db, entity_id)
@@ -151,10 +159,13 @@ def get_alignment_tree(
         raise HTTPException(400, "系统未配置对齐模式，请先在系统设置中初始化")
 
     # 获取本账套所有KPI（账套隔离：仅当前 entity_id，不再返回全实体 KPI）
-    kpis = (db.query(KPIDefinition)
-            .filter(KPIDefinition.entity_id == entity_id, KPIDefinition.status == "active")
-            .order_by(KPIDefinition.kpi_code)
-            .all())
+    kpi_query = (db.query(KPIDefinition)
+                 .filter(KPIDefinition.entity_id == entity_id,
+                         KPIDefinition.status == "active"))
+    # 地图筛选：只缩小 KPI 选择集，不改动任何构建逻辑
+    if map_id is not None:
+        kpi_query = kpi_query.filter(KPIDefinition.map_id == map_id)
+    kpis = kpi_query.order_by(KPIDefinition.kpi_code).all()
     kpi_map = {k.id: k for k in kpis}
 
     # 构建父子关系