Foundry phase 03 · App Router build

Seven lads, one Istanbul, no arguments about money.

Every screen runs the real split, FX and settlement arithmetic. Data is held in memory for now — Postgres, join-code auth and the live geocoders arrive in phase 4.

Screens

• 01Join
  Trip code plus display name. The only unauthenticated route.
• 02Map
  Leaflet and OSM, every location pinned, category filters, add a location.
• 03Vote
  One vote per member per location. Change it and the score moves in place.
• 04Itinerary
  Version 1 is the operator plan, fully pinned. Version history is browsable.
• 05Results
  Tallies, category breakdown, who has voted, spend and balances.
• 06Costs
  GBP or TRY at an agreed rate, reversing entries, settle-up in at most six transfers.

What is real here

• Money is integer minor units end to end. No float touches an amount until it is rendered.
• FX runs through an integer rate_micros captured per expense, so a later rate change cannot rewrite a recorded one.
• Equal split allocates the remainder deterministically, and a reversing entry cancels its original share for share.
• Settlement is greedy cash flow. It zeroes every balance in at most six transfers for seven members — that bound is the guarantee, not a claim of the smallest possible set.
• A negative score ranks a location lower. Nothing is filtered out.
• The itinerary generator runs live: pins first, then descending score, ties broken by distance then id.

What is stubbed

• No Postgres, so no append-only triggers and no server-side session. Vote state lives in localStorage.
• Join takes any code. There is no argon2id hash, no cookie and no rate limit behind it yet.
• Nominatim, Overpass and SearXNG are canned fixtures. The map tile layer is the one genuine outbound call.
• Seed coordinates are hand-placed. The real seed resolves them once and commits fixtures/base-itinerary.json.