Add challenges promotion

backend/app/models/challenge.py

@@ -29,6 +29,12 @@ class ProofType(str, Enum):
     STEAM = "steam"
 
 
+class ChallengeStatus(str, Enum):
+    PENDING = "pending"
+    APPROVED = "approved"
+    REJECTED = "rejected"
+
+
 class Challenge(Base):
     __tablename__ = "challenges"
 
@@ -45,8 +51,13 @@ class Challenge(Base):
     is_generated: Mapped[bool] = mapped_column(Boolean, default=True)
     created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
 
+    # Proposed challenges support
+    proposed_by_id: Mapped[int | None] = mapped_column(ForeignKey("users.id"), nullable=True)
+    status: Mapped[str] = mapped_column(String(20), default="approved")  # pending, approved, rejected
+
     # Relationships
     game: Mapped["Game"] = relationship("Game", back_populates="challenges")
+    proposed_by: Mapped["User"] = relationship("User", foreign_keys=[proposed_by_id])
     assignments: Mapped[list["Assignment"]] = relationship(
         "Assignment",
         back_populates="challenge"