revert: restore production to the state before 730d0bd (PM/RBAC work moved to 'pm')

Their three commits (730d0bd, 5a9b543, 387edfb) reached production by push and
auto-deployed. 387edfb expects a users.username column that the live database does
not have, so POST /api/v1/auth/login was returning HTTP 500. Their schema changes
never applied either (projects still has only id, name, description, start_date,
pm_user_id, created_at), so nothing depends on the reverted code.

This commit sets the tree back to exactly a02b3ea — verified with git diff against
it — while keeping history linear: the work itself is preserved on 'pm' at 387edfb.

backend/app/auth.py

@@ -119,12 +119,10 @@ async def context_from_claims(claims: dict, db: AsyncSession) -> UserContext:
     if not casdoor_id:
         raise UnauthorizedError("توکن فاقد شناسه کاربر است", field="authorization")
 
-    username = str(claims.get("name") or claims.get("preferred_username") or "")
     user = await db.scalar(select(User).where(User.casdoor_id == casdoor_id))
     if user is None:
         user = User(
             casdoor_id=casdoor_id,
-            username=username or None,
             first_name=str(
                 claims.get("firstName")
                 or claims.get("firstname")
@@ -137,12 +135,9 @@ async def context_from_claims(claims: dict, db: AsyncSession) -> UserContext:
         )
         db.add(user)
         await db.flush()
-    elif username and not user.username:
-        user.username = username
-        await db.flush()
 
     project_ids: list = []
-    if user.role in ("supervisor", "pm"):
+    if user.role == "pm":
         projects = (
             await db.execute(
                 select(Project)
@@ -164,7 +159,7 @@ async def context_from_claims(claims: dict, db: AsyncSession) -> UserContext:
 
 
 async def pm_project_ids(db: AsyncSession, user: User) -> list:
-    """Every project id managed by the given PM/supervisor user (oldest first)."""
+    """Every project id managed by the given PM user (oldest first)."""
     rows = (
         await db.execute(
             select(Project.id)