add file and folder_zip svg icons

apps/backend/app/models/skill.py

@@ -8,7 +8,12 @@ from app.models.project_skill import project_skills
 class Skill(Base):
     __tablename__ = "skills"
 
-    id = Column(Integer, primary_key=True, index=True)
+    id = Column(
+        Integer,
+        primary_key=True,
+        index=True,
+        nullable=False
+    )
 
     name = Column(
         String(255),