Upgrade Spring E-Commerce Backend

Key improvements I need:

• Full user-account module: registration, email verification, login/logout, password recovery and profile management, integrated with Spring Security so roles and permissions stay flexible.
• Stateless, scalable sessions backed by Redis; the code must gracefully fall back to the current JDBC session store when Redis is unavailable.
• Any additional backend clean-ups you spot during the work (for instance, refactoring the search service or tightening entity validation) are welcome, provided they are scoped and discussed first.

You will be working with a Maven-built project that currently uses Spring and Hibernate/JPA with Postgresql. The code compiles and deploys, but the new modules are completely missing. I will give you access to the Git repository.

Acceptance will be based on:

1. New user flows exercised through REST and verified by automated tests.
2. Sessions persisting correctly in Redis, visible via the CLI, and surviving application restarts.
3. JUnit tests must be added
4. A concise README explaining environment setup, new endpoints and configuration flags.
5. Must be able to horizontally scale

Expect to collaborate in short pull-request cycles; I review quickly and merge as soon as written tests pass.