Bootstrap Nebulex Cache

Add Nebulex application caching to a Phoenix 1.8 app with a local (single-node) in-memory adapter, sensible GC/memory defaults, a helper module with common cache patterns, and test configuration.

What Gets Created/Configured

1. mix.exs — {:nebulex, "~> 2.6"} dependency
2. lib//cache.ex — Cache module using Nebulex.Adapters.Local
3. lib//cache_helpers.ex — Convenience functions (get-or-store, bulk invalidation, key namespacing)
4. lib//application.ex — Cache added to supervision tree
5. config/config.exs — GC interval, max size, allocated memory defaults
6. config/test.exs — Shorter GC interval for tests
7. test/support/cache_case.ex — (Optional) ExUnit case template that flushes cache between tests
8. test//cache_test.exs — Basic smoke tests

App Name Detection