docs(azure): add RBAC schema documentation

[kunaals]

Summary

• Add documentation for Azure RBAC nodes introduced in PR #1950
• Update mermaid diagram to include RBAC relationships
• Document AzureRoleAssignment, AzureRoleDefinition, and AzurePermissions nodes
• Include example Cypher queries for common security use cases

Nodes Documented

Node	Description
AzureRoleAssignment	Role assignments linking principals (users, groups, service principals) to role definitions at a specific scope
AzureRoleDefinition	Role definitions describing permissions (actions, data actions)
AzurePermissions	Control plane and data plane actions within role definitions

Example Queries Added

• Find all users with the "Owner" role
• Find all principals with write access to storage accounts
• Find service principals with high-privilege roles

Related

• Closes #1735
• Documents implementation from #1950

🤖 Generated with Claude Code

[kunaals]

@Daksh1603 mind giving a quick review here? It's a follow up on your Azure RBAC PR!

[Daksh1603]

@kunaals All looks good! I get a little late on these due to time zone differences. Allow 12 hours, and Ill review the code entirely :D