Participants, context menus, budget rename, file types, UI polish

- Assignment participants: toggle who joins each activity
  - Chips with hover-to-remove (strikethrough effect)
  - Add button with dropdown for available members
  - Avatars in day plan sidebar
  - Side-by-side with reservation in place inspector
- Right-click context menus for places, notes in day plan + places list
- Budget categories can now be renamed (pencil icon inline edit)
- Admin: configurable allowed file types (stored in app_settings)
- File manager shows allowed types dynamically
- Hotel picker: select place + save button (no auto-close)
- Edit pencil opens full hotel popup with all options
- Place inspector: opening hours + files side by side on desktop
- Address clamped to 2 lines, coordinates hidden on mobile
- Category shows icon only on mobile
- Rating hidden on mobile in place inspector
- Time validation: "10" becomes "10:00"
- Climate weather: full hourly data from archive API
- CustomSelect: grouped headers support (isHeader)
- Various responsive fixes

client/src/components/Files/FileManager.jsx

@@ -77,7 +77,7 @@ function SourceBadge({ icon: Icon, label }) {
   )
 }
 
-export default function FileManager({ files = [], onUpload, onDelete, onUpdate, places, reservations = [], tripId }) {
+export default function FileManager({ files = [], onUpload, onDelete, onUpdate, places, reservations = [], tripId, allowedFileTypes }) {
   const [uploading, setUploading] = useState(false)
   const [filterType, setFilterType] = useState('all')
   const [lightboxFile, setLightboxFile] = useState(null)
@@ -229,6 +229,9 @@ export default function FileManager({ files = [], onUpload, onDelete, onUpdate,
           <>
             <p style={{ fontSize: 13, color: 'var(--text-secondary)', fontWeight: 500, margin: 0 }}>{t('files.dropzone')}</p>
             <p style={{ fontSize: 11.5, color: 'var(--text-faint)', marginTop: 3 }}>{t('files.dropzoneHint')}</p>
+            <p style={{ fontSize: 10, color: 'var(--text-faint)', marginTop: 6, opacity: 0.7 }}>
+              {(allowedFileTypes || 'jpg,jpeg,png,gif,webp,heic,pdf,doc,docx,xls,xlsx,txt,csv').toUpperCase().split(',').join(', ')} · Max 50 MB
+            </p>
           </>
         )}
       </div>