feat: update upload functionality and permissions for document handling

- Removed the `upsert` option from the file upload in `uploadDoc` function to prevent unintended overwrites.
- Enhanced German translations in `i18n.js` for better clarity and consistency in the admin interface.
- Added new CSS styles for link interactions to improve user experience in `styles.css`.
- Updated Supabase SQL migration to grant additional permissions for anonymous users to insert and update storage objects, ensuring proper functionality during the booking flow.

Co-authored-by: Copilot <copilot@github.com>

frontend/i18n.js

@@ -180,10 +180,23 @@ export const translations = {
         adminTabDocumentsEn: "Documents",
         adminTabNotes: "Notiz",
         adminTabNotesEn: "Notes",
-        adminTabOrderHistory: "Order History",
+        adminTabOrderHistory: "Bestellungen",
+        adminTabOrderHistoryEn: "Sales Orders",
+        adminPrivateNotes: "Private Notizen",
+        adminPrivateNotesEn: "Private Notes",
+        adminSaveNotes: "Notizen speichern",
+        adminSaveNotesEn: "Save notes",
+        adminNoOrders: "Keine Buchungen gefunden.",
+        adminNoOrdersEn: "No bookings found.",
+        adminKautionPending: "Kaution ausstehend",
+        adminKautionPaid: "Kaution ✓",
+        adminRentalPending: "Miete ausstehend",
+        adminRentalPaid: "Miete ✓",
+        adminCompletePending: "Abgeschlossen offen",
+        adminCompleteDone: "Abgeschlossen ✓",
         adminLifetimeValue: "Gesamtwert aller Buchungen",
         adminLifetimeValueEn: "Lifetime value",
-        adminDownload: "Download",
+        adminDownload: "Herunterladen",
         adminNoDocuments: "Keine Dokumente hochgeladen",
         adminNoDocumentsEn: "No documents uploaded",
         adminIdDoc: "Ausweis / Führerschein",
@@ -395,7 +408,20 @@ export const translations = {
         adminTabDocumentsEn: "Dokumente",
         adminTabNotes: "Notes",
         adminTabNotesEn: "Notiz",
-        adminTabOrderHistory: "Order History",
+        adminTabOrderHistory: "Sales Orders",
+        adminTabOrderHistoryEn: "Bestellungen",
+        adminPrivateNotes: "Private Notes",
+        adminPrivateNotesEn: "Private Notizen",
+        adminSaveNotes: "Save notes",
+        adminSaveNotesEn: "Notizen speichern",
+        adminNoOrders: "No bookings found.",
+        adminNoOrdersEn: "Keine Buchungen gefunden.",
+        adminKautionPending: "Deposit pending",
+        adminKautionPaid: "Deposit ✓",
+        adminRentalPending: "Rental pending",
+        adminRentalPaid: "Rental ✓",
+        adminCompletePending: "Complete open",
+        adminCompleteDone: "Complete ✓",
         adminLifetimeValue: "Lifetime value",
         adminLifetimeValueEn: "Gesamtwert aller Buchungen",
         adminDownload: "Download",