feat(projects): add projects app's basic structure and endpoints

apps/projects/api/permissions.py

@@ -0,0 +1,49 @@
+from rest_framework import permissions
+
+from apps.projects.models import ProjectMembership
+
+
+def get_project_from_obj(obj):
+    """Helper to extract the project from different model types."""
+    # If the object is a Project, it will have a 'workspace' attribute. 
+    # Otherwise, it's a related model (Membership, Rate) and has a 'project' attribute.
+    return obj if hasattr(obj, "workspace") else obj.project
+
+
+class IsProjectMember(permissions.BasePermission):
+    """
+    Allows access only to users who have an active membership in the project.
+    """
+    message = "شما عضو این پروژه نیستید."
+
+    def has_object_permission(self, request, view, obj):
+        if not request.user or not request.user.is_authenticated:
+            return False
+            
+        project = get_project_from_obj(obj)
+        return ProjectMembership.objects.filter(
+            project=project,
+            user=request.user,
+            is_active=True,
+            is_deleted=False
+        ).exists()
+
+
+class IsProjectManager(permissions.BasePermission):
+    """
+    Allows access only to users who are active MANAGERs of the project.
+    """
+    message = "فقط مدیران پروژه مجاز به انجام این عملیات هستند."
+
+    def has_object_permission(self, request, view, obj):
+        if not request.user or not request.user.is_authenticated:
+            return False
+            
+        project = get_project_from_obj(obj)
+        return ProjectMembership.objects.filter(
+            project=project,
+            user=request.user,
+            role=ProjectMembership.Role.MANAGER,
+            is_active=True,
+            is_deleted=False
+        ).exists()