fix(migration): disable transaction for concurrent index creation

PostgreSQL does not allow CREATE INDEX CONCURRENTLY to run inside a
transaction block. This migration now sets $withinTransaction = false
to allow the concurrent index creation to succeed.

Fixes the error: "CREATE INDEX CONCURRENTLY cannot run inside a
transaction block" when running migrations in dev environment.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

database/migrations/2025_06_26_131350_optimize_activity_log_indexes.php

@@ -6,6 +6,12 @@
 
 return new class extends Migration
 {
+    /**
+     * Disable transactions for this migration because CREATE INDEX CONCURRENTLY
+     * cannot run inside a transaction block in PostgreSQL.
+     */
+    public bool $withinTransaction = false;
+
     /**
      * Run the migrations.
      */