Version 1.3.9

* Feature: Rewrote chatbot_endpoint.php with a KB-first hybrid engine.
  - Searches chatbot_knowledge_base table FIRST (FULLTEXT + keyword fallback) before calling Claude.
  - When Claude API is available: injects matching KB entries + live DB data into the system prompt so Claude can give enriched, accurate answers grounded in internal procedures.
  - When Claude is unavailable: answers directly from KB matches with live data injected — never shows generic "trouble connecting" error.
  - Added 10 keyword-based navigation hint rules covering claims, members, benefits, pre-auth, receipts, reimbursements, reports, and corporates.
  - Added error logging (error_log) so API failures are visible in server logs without exposing them to users.
  - Premium context now includes month-to-date premium collected from premium_receipt table.
  - Benefit types, corporate list, and pre-auth data pulled contextually based on message keywords.
