Update backend from polished-with-website branch - new routers (feedback, saved_prompts), updated services and configs

feat: update backend with complete prompt engine v4.0 - Enhanced main.py with request logging, CORS config, embedding preload - Updated config.py with tier-based model routing, rate limits, Stripe stubs - Expanded prompts.py with streaming, voice-enhance, feedback, history, usage endpoints - Added llm_service.py with Groq client pool and key rotation - Updated memory_service.py with passive learning, feedback analysis - Added migrate_embeddings.py for multilingual model migration - Updated schemas.py, auth.py, saved_prompts.py, requirements.txt - Removed prompt_engineering_skeleton directory

small change api

small change api

Update backend: mode-aware enhance, saved prompts CRUD, voice-enhance, feedback endpoint

Merge branch 'main' of https://huggingface.co/spaces/siddhm11/prompt-engine

changes in sim .9 , database:

Update backend/core/config.py

refactor for HF spaces: moved code to backend/

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req docs

initial commit