Phase 002 Execution

Scope

Added the core relational data model for users, vehicles, maintenance schedules, fuel entries, and maintenance entries.
Added validations, factories, and model specs for the new models.
Updated project documentation for confirmed Phase 002 decisions.

Added migrations for users, vehicles, maintenance_schedules, fuel_entries, and maintenance_entries.
Added required fields and foreign keys for all Phase 002 tables.
Added unique indexes for user email, vehicle VIN, vehicle licence plate, and per-vehicle maintenance schedule type.
Added vehicles.active with default true.
Added ActiveRecord models and associations.
Restricted deletion of users and vehicles when historical entries reference them.
Added model validations for presence, uniqueness, numeric bounds, realistic vehicle years, and future-date rejection.
Added VIN normalization to uppercase.
Added maintenance entry validation requiring name to match a vehicle maintenance schedule case-insensitively.
Added factories for all new models.
Added model specs for factories, validations, uniqueness, normalization, schedule matching, and restricted deletion.
Updated AGENTS.md to reflect that bin/ci runs RSpec.
Updated DESIGN.md for corrected names and confirmed data-model rules.

All Phase 002 table fields are required with null: false.
Email and licence plate uniqueness are case-insensitive.
VIN is normalized to uppercase before validation and storage.
MaintenanceSchedule#time_interval stores integer days; display conversion can happen later.
MaintenanceEntry#name is structured and must match a scheduled maintenance type; notes stores free-form details.
Fuel price must be greater than zero; maintenance cost may be zero.
Fuel and maintenance entry dates cannot be in the future.
Vehicles are not deleted; they can be marked inactive later.

Passed: bundle exec rails db:migrate
Initial bundle exec rspec and bin/rubocop failed because spec/models/maintenance_entry_spec.rb had an extra end.
After fixing the syntax error, bundle exec rspec failed because the maintenance_entry factory created matching schedules during negative validation specs.
Updated the factory with an ensure_matching_schedule transient option and disabled it in negative specs.
Passed: bundle exec rspec
Passed: bin/rubocop
Passed: bin/ci