Setup gem "annotaterb" for automatic model schema annotation

[Copilot]

This PR adds the annotaterb gem to automatically keep Rails model files annotated with current database schema information.

What was added

annotaterb gem setup:

• Added annotaterb gem to development dependencies in Gemfile
• Generated .annotaterb.yml configuration file with sensible defaults
• Created lib/tasks/annotate_rb.rake for automatic annotation on database migrations
• Applied initial annotations to existing models and test factories

Key features configured

• Automatic updates: Model annotations are automatically updated when running rails db:migrate in development
• Schema information: Shows table columns, data types, constraints, and indexes
• Factory annotation: Test factories are kept in sync with model changes
• Clean formatting: Uses classified sorting (id, columns, timestamps) for predictable output
• Selective annotation: Focuses on models and tests, excludes controllers and helpers

Before and after

Before - The Org model had no schema documentation:

class Org < ApplicationRecord
  validates :clerk_org_id, presence: true, uniqueness: true
end

After - All models now include comprehensive schema information:

# == Schema Information
#
# Table name: orgs
#
#  id           :bigint           not null, primary key
#  created_at   :datetime         not null
#  updated_at   :datetime         not null
#  clerk_org_id :string           not null
#
# Indexes
#
#  index_orgs_on_clerk_org_id  (clerk_org_id) UNIQUE
#
class Org < ApplicationRecord
  validates :clerk_org_id, presence: true, uniqueness: true
end

The setup improves developer experience by keeping database schema information visible and up-to-date directly in model files, making it easier to understand table structure without checking migrations or schema files.

Fixes #28.

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