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/Photos/PhotoLightbox.jsx

@@ -1,7 +1,9 @@
 import React, { useState, useEffect, useCallback } from 'react'
 import { X, ChevronLeft, ChevronRight, Edit2, Trash2, Check } from 'lucide-react'
+import { useTranslation } from '../../i18n'
 
 export function PhotoLightbox({ photos, initialIndex, onClose, onUpdate, onDelete, days, places, tripId }) {
+  const { t } = useTranslation()
   const [index, setIndex] = useState(initialIndex || 0)
   const [editCaption, setEditCaption] = useState(false)
   const [caption, setCaption] = useState('')
@@ -81,7 +83,7 @@ export function PhotoLightbox({ photos, initialIndex, onClose, onUpdate, onDelet
             <button
               onClick={handleDelete}
               className="p-2 text-white/60 hover:text-red-400 hover:bg-white/10 rounded-lg transition-colors"
-              title="Löschen"
+              title={t('common.delete')}
             >
               <Trash2 className="w-4 h-4" />
             </button>