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/Files/FileManager.jsx

@@ -107,6 +107,23 @@ export default function FileManager({ files = [], onUpload, onDelete, onUpdate,
     noClick: false,
   })
 
+  // Paste support
+  const handlePaste = useCallback((e) => {
+    const items = e.clipboardData?.items
+    if (!items) return
+    const files = []
+    for (const item of items) {
+      if (item.kind === 'file') {
+        const file = item.getAsFile()
+        if (file) files.push(file)
+      }
+    }
+    if (files.length > 0) {
+      e.preventDefault()
+      onDrop(files)
+    }
+  }, [onDrop])
+
   const filteredFiles = files.filter(f => {
     if (filterType === 'pdf') return f.mime_type === 'application/pdf'
     if (filterType === 'image') return isImage(f.mime_type)
@@ -135,7 +152,7 @@ export default function FileManager({ files = [], onUpload, onDelete, onUpdate,
   }
 
   return (
-    <div className="flex flex-col h-full" style={{ fontFamily: "-apple-system, BlinkMacSystemFont, 'SF Pro Text', system-ui, sans-serif" }}>
+    <div className="flex flex-col h-full" style={{ fontFamily: "-apple-system, BlinkMacSystemFont, 'SF Pro Text', system-ui, sans-serif" }} onPaste={handlePaste} tabIndex={-1}>
       {/* Lightbox */}
       {lightboxFile && <ImageLightbox file={lightboxFile} onClose={() => setLightboxFile(null)} />}