feat(migrations): add initial migration setup and performance indexes

- Introduced .pgmrc.json and migrate.json for node-pg-migrate configuration.
- Added multiple migration files to create performance indexes for tasks and related entities.
- Implemented functions for optimized task sorting and manual progress tracking.
- Updated package.json to include migration scripts and dependencies for node-pg-migrate.
- Created README.md for migration guidelines and best practices.

worklenz-backend/.pgmrc.json

@@ -0,0 +1,3 @@
+{
+  "config-file": "migrate.json"
+}