Fix critical migration error (#105)

* chore: improve schema creation and extension setup in migration script

- Added IF NOT EXISTS checks for pgmq schema and extension to ensure idempotency
- Updated function creation script for better stability
- Modified migration checksum file for consistency

* fix: resolve critical migration error preventing installation with previous PGMQ setup

Add new changeset to patch '@pgflow/core' and fix migration issue that blocked installation if
PGMQ was previously installed

Author: jumski

.changeset/silver-candles-pay.md

@@ -0,0 +1,5 @@
+---
+'@pgflow/core': patch
+---
+
+Fix critical migration error that prevented installing if PGMQ was installed previously

pkgs/core/supabase/migrations/20250429164909_pgflow_initial.sql

@@ -1,9 +1,9 @@
 -- Add new schema named "pgflow"
 CREATE SCHEMA "pgflow";
 -- Add new schema named "pgmq"
-CREATE SCHEMA "pgmq";
+CREATE SCHEMA IF NOT EXISTS "pgmq";
 -- Create extension "pgmq"
-CREATE EXTENSION "pgmq" WITH SCHEMA "pgmq" VERSION "1.4.4";
+CREATE EXTENSION IF NOT EXISTS "pgmq" WITH SCHEMA "pgmq" VERSION "1.4.4";
 -- Create "read_with_poll" function
 CREATE FUNCTION "pgflow"."read_with_poll" ("queue_name" text, "vt" integer, "qty" integer, "max_poll_seconds" integer DEFAULT 5, "poll_interval_ms" integer DEFAULT 100, "conditional" jsonb DEFAULT '{}') RETURNS SETOF pgmq.message_record LANGUAGE plpgsql AS $$
 DECLARE

pkgs/core/supabase/migrations/atlas.sum

@@ -1,2 +1,2 @@
-h1:TRBa/BGqiMOCuEzWfl7rP3KeF6wTF8UNWi+OyQ04Uoo=
-20250429164909_pgflow_initial.sql h1:J2retI/QcfsNCP9TVak7J+lxGrtfKNzJTPy6RAGgmco=
+h1:5sJG/Yil5GcUJAlskLtmre1qrjjUGcdEHZ2MNdsYrtE=
+20250429164909_pgflow_initial.sql h1:5K7OqB/vj73TWJTQquUzn+i6H2wWduaW+Ir1an3QYmQ=