docs: Add feature flag naming conventions guide

[talissoncosta]

Summary

Add documentation covering feature flag naming conventions and best practices, including reference to the project-level regex validation setting.

Background

This came up in internal discussion - we have a project setting for enforcing naming conventions via regex, but it's not documented. Additionally, customers frequently ask about naming best practices.

Proposed content

1. Naming conventions best practices

• Importance of consistent naming (features cannot be renamed after creation)
• Self-explanatory names that communicate purpose
• Examples of good vs. bad naming

2. Enforcing naming conventions with regex

• Reference to Project Settings → General → Feature Name RegEx
• How to configure regex validation
• Example regex patterns for common conventions

3. Related: Tag naming conventions

• Cross-reference to existing tagging documentation

Resources

• Best Practices for Feature Flag Management
• 5 Feature Flag Best Practices
• Onboarding deck slide #4

Location

Suggested: docs/best-practices/naming-conventions.md

[emyller]

This reads great. Minor adjustments to scope description:

Importance of consistent naming (can't rename Feature IDs after creation)

- can't rename Feature IDs after creation
+ features cannot be renamed

Suggested patterns (e.g., temp_ prefix for temporary flags)

In theory, a feature flag is meant to be temporary by default, unless it's deemed as a permanent feature in Flagsmith.