Add LPG bi-fuel and hydrogen fuel types

Add petrol_lpg, diesel_lpg and hydrogen to the fuel_type choices, across
the six places that define them: the PocketBase schema, the car form and
detail view in both the Web App and the Phone App, and the two doc
comments that enumerate the values. The Go API needed no change — it
passes fuel_type through as a free string, so PocketBase is the only
validator.

Model the LPG conversions as their own choices rather than a separate
"has LPG" flag: the car runs on either tank, so "petrol + LPG" is what an
owner picks it out as. Order each variant next to its base fuel so the
dropdowns read naturally.

Purely additive — existing rows keep their values and need no migration.
The live PocketBase schema does still need scripts/setup-pocketbase.mjs
re-run before the new choices will save, since its select field allows
only the old four; the script reconciles select values on existing
fields, so re-running migrates it in place.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

API Server/internal/models/models.go

@@ -54,7 +54,7 @@ type Car struct {
 	BrakeFluidSpec      string `json:"brakeFluidSpec"`      // e.g. "DOT 4"
 	CoolantSpec         string `json:"coolantSpec"`         // e.g. "Toyota Super Long Life Coolant"
 
-	FuelType              string `json:"fuelType"`              // petrol | diesel | hybrid | electric
+	FuelType              string `json:"fuelType"`              // petrol | petrol_lpg | diesel | diesel_lpg | hybrid | electric | hydrogen
 	BuildDate             string `json:"buildDate"`             // ISO YYYY-MM-DD (date-only)
 	FirstRegistrationDate string `json:"firstRegistrationDate"` // ISO YYYY-MM-DD (date-only)
 

API Server/scripts/setup-pocketbase.mjs

@@ -245,7 +245,17 @@ const DESIRED = {
     F.text("brake_fluid_spec"),
     F.text("coolant_spec"),
     F.number("current_km"),
-    F.select("fuel_type", ["petrol", "diesel", "hybrid", "electric"]),
+    // Bi-fuel LPG conversions are their own choice rather than a flag: the car
+    // runs on either tank, so "petrol + LPG" is what an owner picks it out as.
+    F.select("fuel_type", [
+      "petrol",
+      "petrol_lpg",
+      "diesel",
+      "diesel_lpg",
+      "hybrid",
+      "electric",
+      "hydrogen",
+    ]),
     F.text("build_date"), // ISO YYYY-MM-DD (date-only; VIN 10th digit ≈ model year)
     F.text("first_registration_date"), // ISO YYYY-MM-DD
     // Owner of this car. Non-cascading on purpose: deleting a user must not