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/Planner/DaysList.jsx

@@ -1,6 +1,7 @@
 import React from 'react'
 import { CalendarDays, MapPin, Plus } from 'lucide-react'
 import WeatherWidget from '../Weather/WeatherWidget'
+import { useTranslation } from '../../i18n'
 
 function formatDate(dateStr) {
   if (!dateStr) return null
@@ -20,6 +21,7 @@ function dayTotal(dayId, assignments) {
 }
 
 export function DaysList({ days, selectedDayId, onSelectDay, assignments, trip }) {
+  const { t } = useTranslation()
   const totalCost = days.reduce((sum, d) => sum + dayTotal(d.id, assignments), 0)
   const currency = trip?.currency || 'EUR'
 
@@ -27,8 +29,8 @@ export function DaysList({ days, selectedDayId, onSelectDay, assignments, trip }
     <div className="flex flex-col h-full">
       {/* Header */}
       <div className="px-4 py-3 border-b border-gray-100 flex-shrink-0">
-        <h2 className="text-sm font-semibold text-gray-700">Tagesplan</h2>
-        <p className="text-xs text-gray-400 mt-0.5">{days.length} Tage</p>
+        <h2 className="text-sm font-semibold text-gray-700">{t('planner.dayPlan')}</h2>
+        <p className="text-xs text-gray-400 mt-0.5">{t('planner.dayCount', { n: days.length })}</p>
       </div>
 
       {/* All places overview option */}
@@ -43,9 +45,9 @@ export function DaysList({ days, selectedDayId, onSelectDay, assignments, trip }
         <MapPin className={`w-4 h-4 flex-shrink-0 ${selectedDayId === null ? 'text-slate-900' : 'text-gray-400'}`} />
         <div>
           <p className={`text-sm font-medium ${selectedDayId === null ? 'text-slate-900' : 'text-gray-700'}`}>
-            Alle Orte
+            {t('planner.allPlaces')}
           </p>
-          <p className="text-xs text-gray-400">Gesamtübersicht</p>
+          <p className="text-xs text-gray-400">{t('planner.overview')}</p>
         </div>
       </button>
 
@@ -54,8 +56,8 @@ export function DaysList({ days, selectedDayId, onSelectDay, assignments, trip }
         {days.length === 0 ? (
           <div className="px-4 py-6 text-center">
             <CalendarDays className="w-8 h-8 text-gray-300 mx-auto mb-2" />
-            <p className="text-xs text-gray-400">Noch keine Tage</p>
-            <p className="text-xs text-gray-300 mt-1">Reise bearbeiten um Tage hinzuzufügen</p>
+            <p className="text-xs text-gray-400">{t('planner.noDays')}</p>
+            <p className="text-xs text-gray-300 mt-1">{t('planner.editTripToAddDays')}</p>
           </div>
         ) : (
           days.map((day, index) => {
@@ -96,7 +98,7 @@ export function DaysList({ days, selectedDayId, onSelectDay, assignments, trip }
                     <div className="flex items-center gap-3 mt-1.5">
                       {placeCount > 0 && (
                         <span className="text-xs text-gray-400">
-                          {placeCount} {placeCount === 1 ? 'Ort' : 'Orte'}
+                          {placeCount === 1 ? t('planner.placeOne') : t('planner.placeN', { n: placeCount })}
                         </span>
                       )}
                       {cost > 0 && (
@@ -124,7 +126,7 @@ export function DaysList({ days, selectedDayId, onSelectDay, assignments, trip }
       {totalCost > 0 && (
         <div className="flex-shrink-0 border-t border-gray-100 px-4 py-3 bg-gray-50">
           <div className="flex items-center justify-between">
-            <span className="text-xs text-gray-500">Gesamtkosten</span>
+            <span className="text-xs text-gray-500">{t('planner.totalCost')}</span>
             <span className="text-sm font-semibold text-gray-800">
               {totalCost.toFixed(2)} {currency}
             </span>