feat(backup): fold .picpeak restore into the Restore wizard's Upload source

Removes the redundant standalone .picpeak card. The wizard's 'Upload
Backup' source now splits into two kinds: '.picpeak backup' (the working
portable restore — renders the upload + destructive-confirm flow inline)
and 'Manifest + files' (legacy, still 'Manifest Upload functionality
coming soon'). en + de strings added.

frontend/src/i18n/locales/de.json

@@ -634,7 +634,16 @@
         "upload": {
           "name": "Backup hochladen",
           "description": "Eine Backup-Datei hochladen",
-          "comingSoon": "Upload-Funktion kommt bald"
+          "comingSoon": "Upload-Funktion kommt bald",
+          "manifestComingSoon": "Manifest-Upload-Funktion kommt bald",
+          "picpeak": {
+            "name": ".picpeak-Backup",
+            "description": "Portables Voll-Backup — stellt alles wieder her (vollständige Überschreibung, Ihr aktuelles Konto bleibt erhalten)."
+          },
+          "manifest": {
+            "name": "Manifest + Dateien",
+            "description": "Ein Manifest und die zugehörigen Backup-Dateien hochladen (Legacy-Format)."
+          }
         },
         "configuration": {
           "s3": "S3-Konfiguration",

frontend/src/i18n/locales/en.json

@@ -3022,7 +3022,16 @@
         "upload": {
           "name": "Upload Backup",
           "description": "Upload a backup file",
-          "comingSoon": "Upload functionality coming soon"
+          "comingSoon": "Upload functionality coming soon",
+          "manifestComingSoon": "Manifest Upload functionality coming soon",
+          "picpeak": {
+            "name": ".picpeak backup",
+            "description": "Portable full backup — restores everything (full override, keeps your current account)."
+          },
+          "manifest": {
+            "name": "Manifest + files",
+            "description": "Upload a manifest and its backup files (legacy format)."
+          }
         },
         "configuration": {
           "s3": "S3 Configuration",