feat(handelsware-datev): Modulseite mit Import, Konten und Einstellungen

- Reiter Import: Vorschau mit neu-Markierung, Buchungsdatum (TTMM) aus dem Dateinamen, Download speichert neue Konten
- Reiter Konten: anlegen, bearbeiten, loeschen mit Rueckfrage, CSV-Import (ersetzt alles, nach Rueckfrage) und -Export
- Reiter Einstellungen nur fuer Administratoren; Texte de/en

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

apps/web/src/messages/en.json

@@ -1698,6 +1698,107 @@
       "saved": "The settings have been saved."
     }
   },
+  "handelswareDatev": {
+    "title": "Merchandise",
+    "description": "Map merchandise sales from Excel to revenue accounts and download them as a DATEV booking file.",
+    "tabs": {
+      "import": "Import",
+      "accounts": "Accounts",
+      "settings": "Settings"
+    },
+    "loading": "Loading …",
+    "notConfigured": {
+      "admin": "The default revenue account and the starting counter account have not been set yet. Without them no accounts can be assigned.",
+      "adminAction": "Go to settings",
+      "user": "An administrator has to set the default revenue account and the starting counter account first."
+    },
+    "import": {
+      "dropPlaceholder": "Drag an Excel file here or click",
+      "dropFormats": ".xlsx, booking text in column A, amount in column B, header text in cell B1",
+      "clear": "Remove file",
+      "checking": "Checking file …",
+      "headerText": "Header text",
+      "exportFilename": "Download file name",
+      "date": "Booking date (DDMM)",
+      "dateHint": "Derived from the file name (last day of the month) and can be changed.",
+      "dateInvalid": "Please enter the date as DDMM, for example 3103 for 31 March.",
+      "columns": {
+        "text": "Booking text",
+        "amount": "Amount",
+        "sh": "D/C",
+        "counter": "Counter account",
+        "date": "Date",
+        "revenue": "Revenue account"
+      },
+      "newBadge": "new",
+      "newSummary": "{count, plural, one {One new account will be saved when you download} other {# new accounts will be saved when you download}}",
+      "noNewAccounts": "All products already have an account.",
+      "totals": "Total debit {debit}, total credit {credit}",
+      "truncated": "Showing the first {shown} of {total} rows. The file contains all rows.",
+      "noRows": "The file contains no data rows.",
+      "rowErrorsTitle": "Faulty rows",
+      "rowErrorLine": "Row {line}",
+      "download": "Download booking file",
+      "downloading": "Creating file …",
+      "downloaded": "The file {filename} has been downloaded. {count, plural, =0 {No new accounts were saved.} one {One new account was saved.} other {# new accounts were saved.}}",
+      "reloadPreview": "Reload preview"
+    },
+    "accounts": {
+      "name": "Name",
+      "counter": "Counter account",
+      "revenue": "Revenue account",
+      "actions": "Actions",
+      "empty": "There are no accounts yet.",
+      "add": "Add",
+      "edit": "Edit",
+      "save": "Save",
+      "cancel": "Cancel",
+      "delete": "Delete",
+      "deleteConfirm": "Really delete account “{name}”?",
+      "deleteYes": "Yes, delete",
+      "namePlaceholder": "Product name",
+      "importCsv": "Import CSV",
+      "exportCsv": "Export CSV",
+      "importConfirm": "{count, plural, =0 {The empty account list is} one {The existing account is} other {All # existing accounts are}} replaced by the content of the file “{file}”. Continue?",
+      "importReplace": "Replace accounts",
+      "importDone": "{count, plural, one {One account was imported.} other {# accounts were imported.}}",
+      "importErrors": "The file contains errors, nothing was changed:",
+      "csvHint": "CSV format: Name;Counter account;Account (semicolon, UTF-8 or Windows-1252).",
+      "invalidNumber": "Counter account and revenue account must be whole numbers.",
+      "nameRequired": "Please enter a name."
+    },
+    "settings": {
+      "intro": "These values apply to all users of your tenant and only have to be set once.",
+      "erloeskonto": "Default revenue account",
+      "erloeskontoHelp": "Assigned to new accounts.",
+      "startGegenkonto": "Starting counter account",
+      "startGegenkontoHelp": "First number handed out when the account list is empty.",
+      "numberInvalid": "Please enter a whole number from 1 to 999999999.",
+      "save": "Save",
+      "saving": "Saving …",
+      "saved": "The settings have been saved."
+    },
+    "errors": {
+      "settingsMissing": "The default revenue account and the starting counter account have not been set yet.",
+      "invalidFile": "The file is not a valid Excel file.",
+      "tooManyRows": "The file contains too many data rows (10000 at most).",
+      "rowErrors": "The file contains faulty rows and cannot be exported.",
+      "noRows": "The file contains no data rows.",
+      "buchungsdatumInvalid": "The booking date must be given as DDMM, for example 3103.",
+      "accountsChanged": "The account list has changed in the meantime. Please upload the file again to refresh the preview.",
+      "nameTaken": "An account with this name already exists.",
+      "umsatzInvalid": "The amount is not a valid number.",
+      "csvErrors": "The CSV file contains errors. Nothing was changed.",
+      "newAccountsInvalid": "The details of the new accounts are invalid.",
+      "nameEmpty": "The name is missing.",
+      "nameTooLong": "The name is too long (120 characters at most).",
+      "gegenkontoInvalid": "The counter account must be a whole number from 1 to 999999999.",
+      "erloeskontoInvalid": "The revenue account must be a whole number from 1 to 999999999.",
+      "missingErloeskonto": "The revenue account is missing and no default revenue account is set.",
+      "duplicateName": "The name appears more than once in the file.",
+      "request": "The request failed. Please try again."
+    }
+  },
   "moduleCategories": {
     "domain-tools": "Domains",
     "security-tools": "Security",