fix: add Matrix bridge deps to compose entrypoint with persistent venv

Adds uv pip install openai mautrix[encryption] to the hermes container
entrypoint, with volume mount at /opt/hermes/.venv for persistence.

Key changes:
- Entrypoint now activates venv and installs Matrix bridge deps before
  running the official entrypoint.sh
- Handles empty-volume first-boot by recreating the venv from scratch
  (matching Dockerfile install steps)
- Persists venv at /mnt/HoardingCow_docker_data/Hermes/venv so pip
  packages survive container recreation

ai/hermes/startup.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+# This file was replaced by inline entrypoint logic in compose.yml
+# See ai/compose.yml hermes.entrypoint for the current implementation.
+echo "startup.sh is obsolete — logic is inline in compose.yml entrypoint"