feat: Remove org-id annotation requirement

[talissoncosta]

Summary

This PR simplifies the plugin configuration by removing the flagsmith.com/org-id annotation requirement. The organization ID is now automatically derived from the project data, reducing the configuration burden on users.

Changes

Core Changes

• Removed org-id annotation requirement: The useFlagsmithUsage hook now only requires project-id
• Automatic org-id derivation: Organization ID is extracted from projectData.organisation
• Simplified API: Removed orgId parameter from useFlagsmithUsage hook

Component Updates

• Updated FlagsmithUsageCard to derive org-id from project data
• Dashboard link construction now uses derived org-id

Developer Experience

• Added /flagsmith-complete demo page: Shows all three components (FlagsTab, Overview Card, Usage Card) on one screen
• Perfect for testing, screenshots, and documentation
• Demonstrates the simplified annotation requirement

Documentation

• Updated README to remove org-id annotation from examples
• Added documentation prompt for contributing Backstage docs to main Flagsmith repo
• Added note explaining automatic org-id derivation

Tests

• Updated useFlagsmithUsage.test.tsx to reflect simplified API
• Removed all org-id parameters from test cases

Before vs After

Before:

annotations:
  flagsmith.com/project-id: '12345'
  flagsmith.com/org-id: '67890'  # Required

After:

annotations:
  flagsmith.com/project-id: '12345'
  # Organization ID automatically derived! ✨

Benefits

1. Simpler configuration: Users only need to provide one annotation instead of two
2. DRY principle: We don't ask users for data we can fetch ourselves
3. Better UX: Less chance of configuration errors
4. Consistent with FlagsTab: Already uses this pattern successfully

Testing

All three components work with only project-id annotation:

• ✅ Feature Flags Tab
• ✅ Overview Card
• ✅ Usage Card

Try it out: yarn start and visit /flagsmith-complete

Breaking Changes

⚠️ This is technically a breaking change to the API signature of useFlagsmithUsage, but:

• The org-id annotation was already documented as "optional"
• Existing users with org-id annotation will continue to work (it's just ignored)
• This simplifies the API and improves the user experience