feat(downloads): change/clear a share link's password from the UI

C-3.7 made a password rotation invalidate outstanding grants, but ShareDialog
only let you set a password at link creation — there was no way to rotate or
clear it afterward, so the protection wasn't reachable. Add a lock control to
each existing link row: set / change / remove the password via the existing
update_link endpoint (which bumps password_version and revokes old grants).

frontend/src/i18n/locales/en/downloads.json

@@ -118,7 +118,12 @@
     "views": "{{n}} views",
     "expiresOn": "expires {{date}}",
     "hasPassword": "password",
-    "downloadable": "downloadable"
+    "downloadable": "downloadable",
+    "setPassword": "Set a password",
+    "changePassword": "Change password",
+    "newPassword": "New password",
+    "savePassword": "Save",
+    "removePassword": "Remove"
   },
   "confirm": {
     "cancelTitle": "Cancel download?",

frontend/src/i18n/locales/hu/downloads.json

@@ -118,7 +118,12 @@
     "views": "{{n}} megtekintés",
     "expiresOn": "lejár: {{date}}",
     "hasPassword": "jelszó",
-    "downloadable": "letölthető"
+    "downloadable": "letölthető",
+    "setPassword": "Jelszó beállítása",
+    "changePassword": "Jelszó módosítása",
+    "newPassword": "Új jelszó",
+    "savePassword": "Mentés",
+    "removePassword": "Törlés"
   },
   "confirm": {
     "cancelTitle": "Megszakítod a letöltést?",