fix: complete Redis cache integration and clean up test layer

fix

fix: deduplicate Celery config fields, fix mypy return-type on task result

feat: add Redis/Celery async job queue for repository analysis

fix

fixed lint

fix(config): expose cache_clear helper to allow reliable test isolation of Settings

fix

fix: reject requests when API_KEY env var is not configured

fix(config): remove hardcoded path and unused fields, make HF-ready

feat: add API key authentication to POST endpoints

fix: replace hardcoded Windows path with cross-platform tempdir

feat: switch LLM back to llama-3.3-70b-instruct

feat: switch LLM to openai/gpt-oss-120b

fix: use Windows-compatible temp path for repository cloning

fix: update pydantic config to V2 style and fix httpx warning

fix: suppress remaining bandit warnings with nosec comments

feat: add core config with pydantic-settings