Restore: Revert codebase to stable May 14th 6 PM state

Restore to latest backup from 13 May - 2026-05-15 17:56

Upgrade: Professional intelligent retrieval pipeline with robust tokenization and LLM query expansion

Migrate from Groq to OpenAI 4o-mini

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Fix database persistence: added sessions volume and robust path handling for /data

feat: add secure admin panel, session store, localStorage tracking