docs: implement Perry Webhook Addon documentation

[D3n3bX]

Description

This PR implements the comprehensive technical documentation for the Perry Webhook Addon, the core Odoo-side component that bridges the ERP with the Perry AI Engine.

Fixes #14

Key Technical Implementations

• Odoo mail.message Hook: Documentation on how the module intercepts communications by overriding the method.
• Non-Blocking Architecture: Detailed explanation of the background threading strategy () and independent database cursors used to ensure a zero-latency UI experience.
• Intelligent Filtering & Anti-Recursion: Explained the logic used to identify private chats and prevent infinite loops (ignoring Perry's own messages).
• Webhook Workflow: Documented the JSON payload structure and the process for committing AI responses back to the Odoo Discuss channel.
• Observability: Details on the Logfire spans used to trace a message from the moment it is typed in Odoo until Perry responds.

This documentation ensures that the integration point between Odoo and the FastAPI ingest engine is clearly defined for future maintenance.