Merge pull request #11 from ivangfr/project-update

chore: upgrade postgres and harden test-endpoints script

test(security): add unit and integration tests for cors, jwt filter, and order controller

refactor(security): use explicit UTF-8 encoding and safer token parsing

chore: upgrade Spring Boot to 4.0.5 and apply minor cleanups

refactor(security): introduce `Role` enum to replace string role constants

chore(ui): configure eslint with lint script and fix violations

docs(agents): update AGENTS.md

feat(user): prevent self-deletion and last-admin deletion

build(api): upgrade Maven wrapper and Spring Boot dependencies

build(ui): upgrade frontend dependencies to latest versions

docs(documentation): reorder demo gifs and update login recordings

docs: add MIT license

feat(ui): improve loading states, form labels, and test coverage

feat(user): sort users by username using derived query method