Merge prod-v8 (multi-project allocation, inter-project transfers) into the all-branches integration

Conflicts (all keep-both):
- init_db.py: v7 added ensure_bot_drafts_table, v8 added
  ensure_project_transfers_table at the same anchor — both functions and
  both startup calls kept
- main.py: same, both ensure calls kept
- ChangeInventoryPage.canSubmit: v9's WITHDRAWAL branch and v8's
  PROJECT_TRANSFER branch — both validation branches kept

backend/app/routers/__init__.py

@@ -15,6 +15,7 @@ from app.routers import (
     material_categories,
     materials,
     pm,
+    project_transfers,
     projects,
     quote_events,
     quotes,
@@ -51,6 +52,7 @@ ROUTERS = [
     standard_conversions.router,
     inventory.router,
     pm.router,
+    project_transfers.router,
     users.router,
     drafts.router,
 ]