feat: v0.16.0 — ISS-005 weight-proportional fuel burn + refuel just enough for the loaded package

Part A: r(F) = k(We + rho*F) L/km, k calibrated so a full tank burns exactly
the old constant; closed forms in lib/sim/movement.ts (fuelAtWeighted,
requiredFuelFor, burnRateConstant, FUEL_DENSITY_KG_PER_L). Catalog gains
emptyWeightKg (ATR72 OEW 9300 kg), exposed in the snapshot. All three burn
call sites (engine landing, state live fuel, fly validation) moved to the
weighted model; old constant-rate fuelAt removed.

Part B: POST /api/planes/{planeId}/refuel takes an optional body
{mode:'full'|'forFlight', packageId} — no body keeps today's fill-to-full
behavior exactly (fuel lands bit-exact on maxFuel); forFlight adds just
enough for the loaded package's destination leg (409 not-loaded/expired/
doesn't-fit, 400 bad body). UI: per-cargo-row 'Refuel' button
(refuel-for-{pkg.id}), market button renamed 'Refuel to full'.

OpenAPI: RefuelRequest schema + optional requestBody + 400 on refuel, fly's
409 description updated, CatalogEntry.emptyWeightKg. Tests: new weighted-burn
suite, forFlight action/route cases (incl. ~7670 km UNNT<->LPPD doesn't-fit),
openapi guards; landing-fuel assertions in engine.test.ts + e2e/actions.spec.ts
use the closed form; the e2e 'return leg unfuelable' scenario reworked — a full
tank now covers the EDDF<->LEZL round trip, so the 409 moves to the second
outbound. New e2e: row Refuel deducts exactly L*price / raises fuel by exactly
L via the endpoint's own response snapshot.

lib/sim/engine.ts

@@ -12,7 +12,7 @@ import {
   type Rng,
   type SeedAirport,
 } from '@/lib/game/seed';
-import { arrivalTimeFor, fuelAt } from './movement';
+import { arrivalTimeFor, fuelAtWeighted } from './movement';
 
 // Server-authoritative sim engine (v0.7.0) — tick-on-read: there is NO background
 // timer. Every read/action endpoint calls tickNow() first; the clock advances by
@@ -131,14 +131,14 @@ export async function deliverPackages(inst: GameDb, clockMs: number): Promise<nu
     const distanceKm = haversineKm(from.lat, from.lon, to.lat, to.lon);
     if (clockMs < arrivalTimeFor(p.departureSimTime, distanceKm, type.speedKmh)) continue;
 
-    // Arrived: progress is exactly 1 here, so remaining fuel is the full-leg burn.
+    // Arrived: progress is exactly 1 here, so remaining fuel is the full-leg weighted burn.
     await inst.db.update(schema.planes)
       .set({
         status: 'available',
         locationIcao: to.icao,
         lat: to.lat,
         lon: to.lon,
-        fuel: fuelAt(p.fuel, type.burnPerKm, distanceKm, 1),
+        fuel: fuelAtWeighted(p.fuel, type.burnPerKm, type.emptyWeightKg, type.maxFuel, distanceKm, 1),
         departureSimTime: null,
         destIcao: null,
       })