Create comprehensive AP Training Guide for Rover ERP implementation engineers

[Copilot]

This PR creates a comprehensive Accounts Payable Implementation Training Guide for Rover ERP, designed specifically for implementation engineers and technical consultants. The guide provides structured, step-by-step guidance for successful AP module deployments based on field-tested best practices.

What's New

New Training Guide Structure at /site/rover/AP-TRAINING/:

• Main Training Guide - Overview, methodology, and complete navigation
• Setup and Configuration - AP Control setup, numbering sequences, and integration configuration
• Vendor Management - Vendor file creation, terms configuration, and data migration strategies
• Data Entry Procedures - Invoice entry workflows, PO matching, and recurring item processing
• Payment Processing - Complete payment workflow from check runs through posting
• Integration Points - GL, PO, inventory, and multi-company integration setup
• Reporting and Inquiries - Standard reports and inquiry functions overview
• Troubleshooting - Field-tested solutions for common implementation challenges
• Go-Live and Support - Implementation phases, success metrics, and ongoing support

Key Features

• Professional, approachable tone suitable for both internal training and customer-facing readiness
• Real-world implementation examples based on anonymized customer scenarios from manufacturing and service companies
• Step-by-step procedures with clear explanations and validation checkpoints
• Comprehensive troubleshooting section with symptoms, causes, and field-tested solutions
• Cross-references to existing Rover ERP documentation throughout all modules
• Implementation methodology covering discovery through go-live and ongoing support

Technical Implementation

• Follows repository contribution guidelines and markdown standards
• Uses consistent PageHeader/PageFooter tags and badge formatting
• Includes cross-reference link from main AP Overview page for discoverability
• All content validated with VuePress build system
• Over 50,000 characters of comprehensive training content across 9 modules

The training guide addresses the complete AP implementation lifecycle and provides implementation engineers with practical guidance to ensure successful customer deployments.

Fixes #173.

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