[FEATURE] Add Transportation Log

Description

A transportation expense is a kind of log entry. It is a Log delegated type, and the Log carries the date.

Fields come from the journal's Transportation Expenses table (Section 10): Date, From, To, Car or Service, Mileage Reimbursement, Parking/Tip, Total.

TransportationExpense

• Is a Log delegated type (required) — the date lives on the Log
• From (String)
• To (String)
• Car or service — two values: car, service
• Mileage reimbursement (Decimal, dollars)
• Parking/tip (Decimal, dollars)

Relationships: Log

Total is not stored. It's mileage reimbursement + parking/tip, computed for display.

UI

Standard scaffolding, plus the pieces that make the expense visible from the log:

• Index — follows the same tabular presentation pattern as app/views/prescriptions/index.html.erb. Copy that structure: the .table-scroll wrapper carrying tabindex="0", role="region" and an aria-label; <th scope="col"> headers; the first cell as <th scope="row"> linking to the show page; or_dash for optional values; table-note spans for secondary detail; and an empty-state paragraph when there are none. Columns: Date, From, To, Car or service, Mileage reimbursement, Parking/tip, Total. Date order.
• Register TransportationExpense in Log's delegated_type list so it appears in the log type selector.
• Add a partial in app/views/transportation_expenses/ that renders the expense's details in a log context.
• Modify the Log index and show to render that partial, dispatching on the loggable type — the same mechanism the Appointment ticket establishes. Keep the generic fallback intact.
• Money formats as currency; blank amounts use or_dash.

Acceptance Criteria

• A user can add, view, edit and delete a transportation expense
• Saving requires a date
• Mileage reimbursement and parking/tip store dollar amounts, not miles
• Total displays as mileage reimbursement + parking/tip, and is not a database column
• The index matches the prescriptions index pattern: scrollable labelled region, scoped table headers, row header linking to show, dashes for blanks, empty state
• TransportationExpense appears in the log type selector
• The log index and show render transportation expense details via the partial
• Log entries of a type with no partial still render via the fallback
• Model tests cover create, the total calculation, and the total when one or both amounts are blank

Notes

• Appointment connection is out of scope. The ERD marks it "optionally connect to appointment"; we're not building that link in this ticket.
• The journal's section header has "If you use a ride service, Company: ___ Phone: ___". That's standing information about the person, not per-trip data. Out of scope here.
• The journal footnote is "Mileage X Government Reimbursement Rate" — the user does that arithmetic themselves and enters the dollar result. We are not storing a mileage rate or doing the conversion.
• Open: how "car or service" is stored — a Rails enum, or a seeded lookup table like MedicationType/AppointmentType. Decide before assigning.

Start with app/views/prescriptions/index.html.erb for the required index pattern, then inspect Log's delegated_type list and the Appointment ticket's log partial mechanism. The app/views/transportation_expenses/ partial, Log index and show, and model tests should cover the stated acceptance criteria, including the unresolved choice between an enum and a lookup table for car or service.