feat(ansible): add mnemosyne db and update ouranos documentation

- Configure mnemosyne database credentials in ansible inventory
- Update postgresql playbook to provision user and database
- Add setup instructions and DB list to documentation

docs/ouranos.md

@@ -72,7 +72,7 @@ King of the Fairies orchestrating containers and managing MCP infrastructure.
 Intelligent and resourceful — the reliability of relational databases.
 
 - PostgreSQL 17 (port 5432)
-- Databases: `arke`, `anythingllm`, `gitea`, `hass`, `lobechat`, `mcp_switchboard`, `nextcloud`, `openwebui`, `periplus`, `spelunker`
+- Databases: `arke`, `anythingllm`, `gitea`, `hass`, `lobechat`, `mcp_switchboard`, `mnemosyne`, `nextcloud`, `openwebui`, `periplus`, `spelunker`
 
 ### ariel — Graph Database
 
@@ -297,6 +297,35 @@ ansible-playbook site.yml
 ansible-playbook sandbox_down.yml
 ```
 
+### Python Virtual Environment Setup
+
+The Ansible automation requires a Python virtual environment with the `ansible` package installed. Create and activate the environment from the `~` directory:
+
+```bash
+# Create virtual environment
+cd ~
+python3 -m venv env/ouranos
+
+# Activate environment
+source ~/env/ouranos/bin/activate
+
+# Install Ansible
+pip install ansible
+pip install ansible-core
+pip install ansible-community.postgresql
+```
+
+### Ansible Playbook Syntax Check
+
+Before running playbooks, use the `apsc.sh` utility (in PATH) to quickly validate YAML syntax:
+
+```bash
+# From the ansible directory
+apsc.sh
+
+# This will check all YAML files in the current directory for syntax errors
+```
+
 ### Terraform Workflow
 
 1. **Define** — Containers, networks, and resources in `*.tf` files