Add PolicyHelpers macro for standard user policies

Encapsulate two-tier policy pattern (bypass + HasPermission).
Promote consistency across resource policy definitions.

lib/mv/authorization/policy_helpers.ex

@@ -0,0 +1,40 @@
+defmodule Mv.Authorization.PolicyHelpers do
+  @moduledoc """
+  Policy helpers for consistent bypass vs HasPermission patterns.
+
+  ## Pattern: READ Bypass + UPDATE HasPermission
+
+  For resources with scope :own/:linked permissions:
+  - READ: Use bypass with expr() for auto_filter
+  - UPDATE/CREATE/DESTROY: Use HasPermission for scope evaluation
+
+  ## Usage
+
+      use Mv.Authorization.PolicyHelpers
+
+      policies do
+        # Standard pattern for User resource
+        standard_user_policies()
+      end
+
+  ## Why This Pattern?
+
+  See `docs/policy-bypass-vs-haspermission.md` for detailed explanation.
+  """
+
+  defmacro standard_user_policies do
+    quote do
+      # READ: Bypass for auto_filter
+      bypass action_type(:read) do
+        description "Users can read their own records"
+        authorize_if expr(id == ^actor(:id))
+      end
+
+      # UPDATE/CREATE/DESTROY: HasPermission
+      policy action_type([:update, :create, :destroy]) do
+        description "Check permissions from role"
+        authorize_if Mv.Authorization.Checks.HasPermission
+      end
+    end
+  end
+end