v2.5.7: Reservation overhaul, Day Detail Panel, i18n, paste support, auto dark mode

BREAKING: Reservations have been completely rebuilt. Existing place-level
reservations are no longer used. All reservations must be re-created via
the Bookings tab. Your trips, places, and other data are unaffected.

Reservation System (rebuilt from scratch):
- Reservations now link to specific day assignments instead of places
- Same place on different days can have independent reservations
- New assignment picker in booking modal (grouped by day, searchable)
- Removed day/place dropdowns from booking form
- Reservation badges in day plan sidebar with type-specific icons
- Reservation details in place inspector (only for selected assignment)
- Reservation summary in day detail panel

Day Detail Panel (new):
- Opens on day click in the sidebar
- Detailed weather: hourly forecast, precipitation, wind, sunrise/sunset
- Historical climate averages for dates beyond 16 days
- Accommodation management with check-in/check-out, confirmation number
- Hotel assignment across multiple days with day range picker
- Reservation overview for the day

Places:
- Places can now be assigned to the same day multiple times
- Start time + end time fields (replaces single time field)
- Map badges show multiple position numbers (e.g. "1 · 4")
- Route optimization fixed for duplicate places
- File attachments during place editing (not just creation)
- Cover image upload during trip creation (not just editing)
- Paste support (Ctrl+V) for images in trip, place, and file forms

Internationalization:
- 200+ hardcoded German strings translated to i18n (EN + DE)
- Server error messages in English
- Category seeds in English for new installations
- All planner, register, photo, packing components translated

UI/UX:
- Auto dark mode (follows system preference, configurable in settings)
- Navbar toggle switches light/dark (overrides auto)
- Sidebar minimize buttons z-index fixed
- Transport mode selector removed from day plan
- CustomSelect supports grouped headers (isHeader option)
- Optimistic updates for day notes (instant feedback)
- Booking cards redesigned with type-colored headers and structured details

Weather:
- Wind speed in mph when using Fahrenheit setting
- Weather description language matches app language

Admin:
- Weather info panel replaces OpenWeatherMap key input
- "Recommended" badge styling updated

client/src/components/Map/RouteCalculator.js

@@ -9,7 +9,7 @@ const OSRM_BASE = 'https://router.project-osrm.org/route/v1'
  */
 export async function calculateRoute(waypoints, profile = 'driving') {
   if (!waypoints || waypoints.length < 2) {
-    throw new Error('Mindestens 2 Wegpunkte erforderlich')
+    throw new Error('At least 2 waypoints required')
   }
 
   const coords = waypoints.map(p => `${p.lng},${p.lat}`).join(';')
@@ -18,13 +18,13 @@ export async function calculateRoute(waypoints, profile = 'driving') {
 
   const response = await fetch(url)
   if (!response.ok) {
-    throw new Error('Route konnte nicht berechnet werden')
+    throw new Error('Route could not be calculated')
   }
 
   const data = await response.json()
 
   if (data.code !== 'Ok' || !data.routes || data.routes.length === 0) {
-    throw new Error('Keine Route gefunden')
+    throw new Error('No route found')
   }
 
   const route = data.routes[0]
@@ -74,20 +74,23 @@ export function optimizeRoute(places) {
   const visited = new Set()
   const result = []
   let current = valid[0]
-  visited.add(current.id)
+  visited.add(0)
   result.push(current)
 
   while (result.length < valid.length) {
-    let nearest = null
+    let nearestIdx = -1
     let minDist = Infinity
-    for (const place of valid) {
-      if (visited.has(place.id)) continue
+    for (let i = 0; i < valid.length; i++) {
+      if (visited.has(i)) continue
       const d = Math.sqrt(
-        Math.pow(place.lat - current.lat, 2) + Math.pow(place.lng - current.lng, 2)
+        Math.pow(valid[i].lat - current.lat, 2) + Math.pow(valid[i].lng - current.lng, 2)
       )
-      if (d < minDist) { minDist = d; nearest = place }
+      if (d < minDist) { minDist = d; nearestIdx = i }
     }
-    if (nearest) { visited.add(nearest.id); result.push(nearest); current = nearest }
+    if (nearestIdx === -1) break
+    visited.add(nearestIdx)
+    current = valid[nearestIdx]
+    result.push(current)
   }
   return result
 }
@@ -103,7 +106,7 @@ function formatDuration(seconds) {
   const h = Math.floor(seconds / 3600)
   const m = Math.floor((seconds % 3600) / 60)
   if (h > 0) {
-    return `${h} Std. ${m} Min.`
+    return `${h} h ${m} min`
   }
-  return `${m} Min.`
+  return `${m} min`
 }