feat: add role/permission system with tests support

- Add Role model with 17 default permissions
- Add init_wizard to create admin/guest roles on first startup
- Protect admin role from modification/deletion via API
- Fix MilestoneCreate schema (project_id optional)
- Fix delete role to clean up role_permissions first
- Add check_project_role RBAC function

app/api/routers/milestones.py

@@ -54,6 +54,8 @@ def create_milestone(project_id: int, milestone: schemas.MilestoneCreate, db: Se
     milestone_code = f"{project_code}:{next_num:05x}"
     
     data = milestone.model_dump()
+    # Remove project_id from data if present (it's already in the URL path)
+    data.pop('project_id', None)
     # Handle JSON fields
     if data.get("depend_on_milestones"):
         data["depend_on_milestones"] = json.dumps(data["depend_on_milestones"])