Model factories for tests and seeding

[eaguad1337]

Problem

There is no factory pattern for generating model instances or realistic test data. Seeding is written by hand.

Proposal

Model factories:

• Factory classes bound to models with a definition() returning attributes.
• Faker integration for realistic values.
• States (named attribute overrides), relationship helpers, and count() for batches.
• Usable from both tests and seeders.
• make:factory command + stub.

Scope

Factory base, discovery/registry, states, relationships, faker, command + stub.

Definition of Done

• Implementation integrating with ORM seeding.
• pytest covers single/batch creation, states, and relationships (suite green).
• Docs page + nav entry.
• Release notes entry.