feat: add self-hosted memory providers (OpenViking, Honcho, Holographic)

- Add OpenViking service (knowledge graph) using official GHCR image
- Add Honcho stack (user modeling): API + PostgreSQL pgvector + Redis
- Add Holographic config to Hermes (local SQLite, no server needed)
- Hermes: install httpx for OpenViking client
- Hermes: auto-generate config.yaml + honcho.json on first boot
- All data 100% local, zero cloud dependencies

ai/.env.example

@@ -0,0 +1,8 @@
+# AI Stack Environment Variables
+# Copy to .env and set your values
+
+# Required: OpenRouter API key for Hermes agent
+OPENROUTER_API_KEY=sk-or-v1-your-key-here
+
+# Memory providers (internal Docker network — usually no changes needed)
+OPENVIKING_ENDPOINT=http://openviking:1933