feat(pm): multi-project PMs (1:N) with project switching, scoping validation and org multi-select

Task 1 — PM 1:N + access-loss handling:
- projects.pm_user_id had no UNIQUE constraint (verified live + in schema); added a lookup index via init_db
- auth: UserContext.project_ids = every project of a PM (oldest first); project_id stays the first for compatibility
- GET /users/me/projects — assigned projects of the caller (drives the switcher + revocation validation)
- login / /users/me / /users list now return the full projects array per user
- /inventory/* and /pm/* scopes accept an explicit ?project_id=… and verify the PM manages it (403 otherwise); without the param they fall back to the first project; admin/manager use it as an optional filter
- POST /users/{id}/project is multi-aware: assigns one project (replacing that project's previous PM) and KEEPS the user's other assignments; null clears all
- PATCH /projects/{id} accepts pm_user_id (admin / procurement manager only)
- frontend: auth store holds projects + the active project (persisted via the existing localStorage store); RequirePmProjects re-validates on load, falls back when the active project was revoked, and shows a dedicated no-projects screen with logout (no redirect loop, no re-auth)
- Panels menu: «مدیریت انبار» gets a ChevronDown accordion listing the PM's projects with «✓ فعلی»; selecting one switches only the active project and reloads the section data
- inventory/pm API calls now send the active project_id explicitly

Task 2 — Organization page:
- new searchable ProjectMultiSelect combobox (chips with ×, live Persian filtering via normalize, assigned projects hidden) replaces the single select for PM users
- add = PATCH project pm_user_id=<user>; × = pm_user_id=null; table and project cards sync immediately; RBAC unchanged (role column admin-only, combobox editable for admin + procurement manager)

Verified locally: 17 scripted checks — multi-project assignment without unique conflicts, /users/me/projects, explicit project_id authorization (foreign project 403 on /inventory, /pm/on-the-way, /pm/receipts), PM blocked from pm_user_id changes, legacy assign endpoint keeps other assignments, revocation removes the project from the list, zero-project PM gets an empty list and a guarded inventory endpoint. All test data cleaned up afterwards.

frontend/src/pages/Inventory/ArrivalsPage.tsx

@@ -33,9 +33,11 @@ export function ArrivalsPage() {
 
   const load = useCallback(async () => {
     try {
+      const activeProject = isPM ? user?.project_id || undefined : undefined;
       const [arr, whs] = await Promise.all([
-        apiV26.pm.onTheWay(),
-        apiV26.warehouses.list(isPM ? user?.project_id || undefined : undefined),
+        // پروژه‌ی فعال صریحاً ارسال می‌شود؛ بک‌اند تخصیص PM را بررسی می‌کند
+        apiV26.pm.onTheWay(activeProject),
+        apiV26.warehouses.list(activeProject),
       ]);
       setItems(arr);
       setWarehouses(whs);
@@ -186,7 +188,7 @@ export function ArrivalsPage() {
           item_decision_id: it.item_decision_id,
           received_qty: draftReceivedOf(it),
           allocations,
-        });
+        }, isPM ? user?.project_id || undefined : undefined);
       }
       toast.success("رسید (کامل یا جزیی) ثبت شد و به انبارها وارد شد ✓ — اقلام باقی‌مانده همچنان در راه هستند");
       // همگام‌سازی با دفتر تدارکات: store پیشنهادها را تازه کن تا کارت‌های