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

server/src/scheduler.js

@@ -55,9 +55,9 @@ async function runBackup() {
       if (fs.existsSync(uploadsDir)) archive.directory(uploadsDir, 'uploads');
       archive.finalize();
     });
-    console.log(`[Auto-Backup] Erstellt: ${filename}`);
+    console.log(`[Auto-Backup] Created: ${filename}`);
   } catch (err) {
-    console.error('[Auto-Backup] Fehler:', err.message);
+    console.error('[Auto-Backup] Error:', err.message);
     if (fs.existsSync(outputPath)) fs.unlinkSync(outputPath);
     return;
   }
@@ -77,11 +77,11 @@ function cleanupOldBackups(keepDays) {
       const stat = fs.statSync(filePath);
       if (stat.birthtimeMs < cutoff) {
         fs.unlinkSync(filePath);
-        console.log(`[Auto-Backup] Altes Backup gelöscht: ${file}`);
+        console.log(`[Auto-Backup] Old backup deleted: ${file}`);
       }
     }
   } catch (err) {
-    console.error('[Auto-Backup] Bereinigungsfehler:', err.message);
+    console.error('[Auto-Backup] Cleanup error:', err.message);
   }
 }
 
@@ -93,13 +93,13 @@ function start() {
 
   const settings = loadSettings();
   if (!settings.enabled) {
-    console.log('[Auto-Backup] Deaktiviert');
+    console.log('[Auto-Backup] Disabled');
     return;
   }
 
   const expression = CRON_EXPRESSIONS[settings.interval] || CRON_EXPRESSIONS.daily;
   currentTask = cron.schedule(expression, runBackup);
-  console.log(`[Auto-Backup] Geplant: ${settings.interval} (${expression}), Aufbewahrung: ${settings.keep_days === 0 ? 'immer' : settings.keep_days + ' Tage'}`);
+  console.log(`[Auto-Backup] Scheduled: ${settings.interval} (${expression}), retention: ${settings.keep_days === 0 ? 'forever' : settings.keep_days + ' days'}`);
 }
 
 // Demo mode: hourly reset of demo user data