feat: add deposit and weekend km allowance to vehicles, update migrations and booking flow

Co-authored-by: Copilot <copilot@github.com>

frontend/i18n.js

@@ -133,7 +133,6 @@ export const translations = {
         adminNewVehicle: "Neues Fahrzeug",
         adminAllVehicles: "Alle Fahrzeuge",
         adminPhotoUpload: "Foto hochladen (JPG/PNG/WebP, max 50 MB)",
-        adminPhotoUrl: "Foto-URL (wird automatisch gesetzt nach Upload)",
         adminBrand: "Marke",
         adminModel: "Modell",
         adminPower: "PS",
@@ -169,6 +168,8 @@ export const translations = {
         adminReceived: "Eingang",
         adminVehicleTab: "Fahrzeug",
         adminPeriod: "Zeitraum",
+        adminKaution: "Kaution (€)",
+        adminMaxKmWeekend: "Max. km/Wochenendtag",
     },
     en: {
         navCars: "Fleet",
@@ -303,7 +304,6 @@ export const translations = {
         adminNewVehicle: "New vehicle",
         adminAllVehicles: "All vehicles",
         adminPhotoUpload: "Upload photo (JPG/PNG/WebP, max 50 MB)",
-        adminPhotoUrl: "Photo URL (auto-set after upload)",
         adminBrand: "Brand",
         adminModel: "Model",
         adminPower: "HP",
@@ -339,6 +339,8 @@ export const translations = {
         adminReceived: "Received",
         adminVehicleTab: "Vehicle",
         adminPeriod: "Period",
+        adminKaution: "Deposit (€)",
+        adminMaxKmWeekend: "Max. km/weekend day",
     },
 };