feat: add configurable cache backend (redis/memcache)

[CrazyTodd-one]

Pull Request

Description

Add configurable cache backend to support Redis/Memcache in production (#259).

The API currently uses InMemoryBackend which doesn't share cache across workers and has no size bounds. This adds CACHE_BACKEND and CACHE_URL environment variables to switch between inmemory, redis, or memcache.

Changes:

• main.py: match/case backend selection based on config
• server.conf: added CACHE_BACKEND and CACHE_URL config options
• pyproject.toml: added redis extra to fastapi-cache2

Defaults to inmemory — no breaking changes. Set CACHE_BACKEND=redis and CACHE_URL=redis://host:6379 to switch.

Fixes #259

How Has This Been Tested?

• Unit tests pass (17/17)
• Default inmemory path unchanged
• Verified redis/memcache imports resolve with updated deps

Checklist:

• My code follows OCF's coding style guidelines
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked my code and corrected any misspellings