procmail2notmuch: add sql rule loader

server/migrations/20250419202131_email-rules.down.sql

@@ -0,0 +1,3 @@
+DROP TABLE IF NOT EXISTS email_rule;
+
+-- Add down migration script here

server/migrations/20250419202131_email-rules.up.sql

@@ -0,0 +1,5 @@
+CREATE TABLE IF NOT EXISTS email_rule (
+    id integer NOT NULL GENERATED ALWAYS AS IDENTITY,
+    sort_order integer NOT NULL,
+    rule jsonb NOT NULL
+);