chore(pm): vendor the Aramesh/PM platform under pm/ (squash of Aramesh/PM @ 91f3271)

The PM panel (PmPanelPage -> iframe /pm/) needs the project-management
platform served at /pm/ on the ERP domain. Source: org repo Aramesh/PM,
branch feature/project-management-platform. Update via:
git subtree pull --prefix=pm aramesh-pm feature/project-management-platform --squash

pm/backend/app/main.py

@@ -0,0 +1,79 @@
+"""PM — Project Management operational layer. FastAPI entrypoint."""
+import asyncio
+import logging
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+from sqlalchemy import select
+
+from app.config import settings
+from app.db import SessionFactory, engine
+from app.dev_accounts import ensure_demo_accounts, ensure_demo_assignments
+from app.errors import install_error_handlers
+from app.models import Base, PMUser
+from app.routers import auth, dashboard, files, projects, qc, tasks, users
+from app.security import hash_password
+
+logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s %(name)s — %(message)s")
+logging.getLogger("httpx").setLevel(logging.WARNING)
+
+
+async def _ensure_admin() -> None:
+    """Seed the local admin user (role: project_manager) from env on first boot."""
+    async with SessionFactory() as db:
+        existing = await db.scalar(select(PMUser).where(PMUser.username == settings.ADMIN_USER))
+        if existing is None:
+            db.add(
+                PMUser(
+                    username=settings.ADMIN_USER,
+                    password_hash=hash_password(settings.ADMIN_PASSWORD),
+                    display_name="مدیر سیستم",
+                    role="project_manager",
+                )
+            )
+            await db.commit()
+            logging.getLogger("pm.boot").info("seeded admin user %s", settings.ADMIN_USER)
+        # dev role switcher: demo accounts for the dashboard picker
+        await ensure_demo_accounts(db)
+
+
+@asynccontextmanager
+async def lifespan(_: FastAPI):
+    if settings.DEV_ROLE_SWITCH:
+        logging.getLogger("pm.boot").warning(
+            "PM_DEV_ROLE_SWITCH is ON — /auth/dev-login issues tokens without a password. "
+            "Set PM_DEV_ROLE_SWITCH=false for production."
+        )
+    async with engine.begin() as conn:
+        from app.schema_sync import drop_legacy, ensure_schema
+
+        await drop_legacy(conn)
+        await conn.run_sync(Base.metadata.create_all)
+        await ensure_schema(conn)
+    await _ensure_admin()
+    asyncio.create_task(_init_demo_assignments())
+    yield
+
+
+async def _init_demo_assignments() -> None:
+    await asyncio.sleep(1)
+    try:
+        async with SessionFactory() as db:
+            await ensure_demo_assignments(db)
+    except Exception:  # noqa: BLE001
+        logging.getLogger("pm.boot").exception("demo assignment failed")
+
+
+app = FastAPI(title="PM — Construction Project Management Platform", version="1.0.0", lifespan=lifespan)
+
+API_V1_PREFIX = "/api/v1"
+for module in (auth, users, dashboard, projects, tasks, qc, files):
+    app.include_router(module.router, prefix=API_V1_PREFIX)
+
+
+@app.get("/health")
+async def health():
+    return {"status": "ok", "service": "pm-api"}
+
+
+install_error_handlers(app)