Knowledge base unavailable after single-host deployment — ChromaDB connected but KB not initialized #3094

Problem

/knowledge/categories returns empty/404 after fresh deployment. ChromaDB is running on port 8100 and responding to heartbeats, but:

• Backend health reports knowledge_base: unavailable
• Knowledge base singleton failed to initialize on startup
• /api/knowledge/test_categories_main returns 404

Root Cause

1. ChromaDB port changed from 8000→8100 but backend started before config was applied
2. Knowledge base initialization is non-recoverable on startup failure
3. /var/lib/autobot ownership was autobot-ai not autobot

Fix Needed

• Knowledge base should retry connection to ChromaDB on-demand, not just at startup
• Or: restart backend after ChromaDB is confirmed running
• Backend role should ensure /var/lib/autobot is owned by autobot

Discovered During

Single-host deployment verification 2026-03-31