Add LLM endpoints, web frontend, and rate limiting config

- Added OpenAI-compatible LLM endpoints to API backend - Introduced web
frontend with Jinja2 templates and static assets - Implemented API proxy
routes in web service - Added sample db.json data for items, users,
orders, reviews, categories, llm_requests - Updated ADC and Helm configs
for separate AI and standard rate limiting - Upgraded FastAPI, Uvicorn,
and added httpx, Jinja2, python-multipart dependencies - Added API
configuration modal and client-side JS for web app

api/requirements.txt

@@ -1,3 +1,4 @@
-fastapi==0.104.1
-uvicorn[standard]==0.24.0
+fastapi==0.109.0
+uvicorn==0.27.0
 pydantic==2.5.0
+httpx==0.26.0