feat(places): link an expense to a place, the way bookings already do (#1917)

* feat(places): link an expense to a place, the way bookings already do

Recording what a museum ticket or a guided tour cost meant leaving the place,
opening the Costs tab and typing it in again — while a booking has had a Costs
block in its own form all along.

The place form now carries that block. Same component, same flow: with nothing
linked it offers Create expense, which saves the place and then opens the Costs
editor for a new expense pointing at it; once linked it shows the expense with
edit and remove. budget_items gains place_id beside the reservation_id it
already had, with the same nullable FK and the same ON DELETE SET NULL. Desktop
and phone both, and the mobile editor carries the link through its own save path
rather than the desktop one.

The expense belongs to the place, not to a day assignment, so a place sitting on
five days is not five tickets. Hanging it off the assignment would have meant
adding a place to three days quietly creating three expenses and removing a day
quietly deleting one.

Deleting a place takes its expense with it in the same transaction and announces
it, on every path that deletes a place: REST, both MCP tools and the plugin RPC.

Closes #1298

* test(places): teach the RPC stubs about linkedExpenseIds

The delete paths read the linked expense before the place is gone, so the two
hand-built PlacesService stubs threw on the new method instead of reaching the
hook, the remove and the broadcast — four failures out of one missing line.

wiki/Reservations-and-Bookings.md

@@ -73,7 +73,7 @@ Click **Add** (or the + button) in the Reservations panel. Fill in the form:
 9. **Hotel-specific fields** — shown only for Hotel type, immediately after status: hotel place, check-in day, check-out day, check-in time (window start and end), and check-out time. See [Accommodations](Accommodations)
 10. **Notes**
 11. **Files** — attach from your device (PDF, Word documents, text files, images) or link an existing trip file. Files added before saving are uploaded automatically after the reservation is created
-12. **Price and budget category** — shown only when the Budget addon is enabled. Entering a price greater than zero automatically creates a linked budget entry. See [Budget-Tracking](Budget-Tracking)
+12. **Costs** — shown only when the Budget addon is enabled. Instead of a price field, the form carries a **Create expense** button: it saves the booking and then opens the Costs editor for a new expense linked to it, so the expense gets a payer, a split and a date like any other. Once linked, the block shows that expense with edit and remove actions. See [Budget-Tracking](Budget-Tracking)
 
 <!-- TODO: screenshot: Create Reservation modal -->