fix(auth): auth deps use their own DB session; smoke suites made dataset-independent

RUNTIME BUG (caught by live smoke tests): the global auth dependency
queried the request-scoped session, auto-beginning its transaction — any
endpoint opening 'async with db.begin()' afterwards crashed with
'transaction already begun' (POST /materials 500). get_current_user /
get_actor now resolve in a short-lived session (expire_on_commit=False
keeps the context usable detached); inventory/pm scopes keep passing the
request session explicitly.

Smoke suites rewritten against CURRENT contracts:
- assertions are behavior-based (shapes, envelopes, filters), no magic
  seed counts; dynamic lookups instead of hard-coded names/ids
- rerun-tolerant: tolerate 409-on-create by reusing prior artifacts
- aligned with current rules: revert blocked after inventory receipts
  (v2.6), attachments allowed in every status, termsheets optional at
  quote level
- SMOKE_USER/SMOKE_PASSWORD env for login (default tester/123456)

Verified on a fresh volume: migration + audit_log bootstrap, Casdoor
seed (bcrypt), demo data, and 29+76+61 smoke checks all green.

backend/app/auth.py

@@ -26,7 +26,7 @@ from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.config import settings
-from app.db.engine import get_db
+from app.db.engine import AsyncSessionLocal
 from app.models.procurement import Project, User
 from app.utils.errors import (
     ForbiddenError,
@@ -170,11 +170,16 @@ async def pm_project_ids(db: AsyncSession, user: User) -> list:
     return list(rows)
 
 
-async def get_optional_user(request: Request, db: AsyncSession) -> UserContext | None:
+async def get_optional_user(request: Request, db: AsyncSession | None = None) -> UserContext | None:
     """Resolve the caller from the Casdoor Bearer token, or None when absent.
 
     Raises UnauthorizedError for a present-but-invalid token; callers decide
     their own fallback only for the no-token case (e.g. dev headers).
+
+    IMPORTANT: when ``db`` is omitted (pure auth-dependency usage), a
+    short-lived session of its own is used — querying the REQUEST session
+    here would auto-begin its transaction and break endpoints that open
+    explicit ``async with db.begin()`` blocks afterwards.
     """
     auth = request.headers.get("authorization", "")
     if not auth.lower().startswith("bearer "):
@@ -182,13 +187,22 @@ async def get_optional_user(request: Request, db: AsyncSession) -> UserContext |
     token = auth.split(" ", 1)[1].strip()
     if not token:
         return None
+    if db is None:
+        async with AsyncSessionLocal() as own_session:
+            claims = await _verify_token(token)
+            return await context_from_claims(claims, own_session)
     claims = await _verify_token(token)
     return await context_from_claims(claims, db)
 
 
-async def get_current_user(request: Request, db: AsyncSession = Depends(get_db)) -> UserContext:
-    """Require a valid Casdoor token (401 missing/invalid; 403 unprovisioned)."""
-    ctx = await get_optional_user(request, db)
+async def get_current_user(request: Request) -> UserContext:
+    """Require a valid Casdoor token (401 missing/invalid; 403 unprovisioned).
+
+    Resolves the user in its own session (see get_optional_user) so the
+    global auth dependency never interferes with an endpoint's explicit
+    transaction handling.
+    """
+    ctx = await get_optional_user(request)
     if ctx is None:
         raise UnauthorizedError("احراز هویت لازم است — توکن Casdoor ارسال کنید")
     if ctx.role is None: