feat(07): add CSV format help text and Exchange 401 diagnostic hints

- CSV import dialog shows format line + example before mode selection
- Exchange connection test: on 401, inline hint lists common causes
  (wrong credentials, domain format, username prefix, O365 not supported)
- Both de/en translations updated

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/src/app/(portal)/modules/dkv-fleet/settings/components/CsvImportButton.tsx

@@ -111,6 +111,11 @@ export function CsvImportButton({ onImported }: CsvImportButtonProps) {
       {/* Import mode inline dialog (below button, per UI-SPEC) */}
       {showDialog && selectedFile && (
         <div className="absolute right-0 top-10 z-30 w-80 rounded border border-border bg-card p-4 shadow-md">
+          <div className="mb-3 rounded bg-muted/50 px-3 py-2 text-xs text-muted-foreground space-y-0.5">
+            <p>{t('csvFormatHelp')}</p>
+            <p className="font-mono">{t('csvFormatExample')}</p>
+          </div>
+
           <p className="text-sm font-medium text-foreground mb-3">
             {t('importMode')}
           </p>

apps/web/src/app/(portal)/modules/dkv-fleet/settings/components/InboxConfigForm.tsx

@@ -507,20 +507,36 @@ export function InboxConfigForm() {
 
       {/* Inline test feedback */}
       {testResult !== null && (
-        <p
-          className="text-sm"
-          style={{
-            color: testResult.success
-              ? 'oklch(0.40 0.15 148)'
-              : 'var(--destructive)',
-          }}
-        >
-          {testResult.success
-            ? t('form.testSuccess')
-            : t('form.testFailed', {
-                error: testResult.message ?? 'Unbekannter Fehler',
-              })}
-        </p>
+        <div className="space-y-1">
+          <p
+            className="text-sm"
+            style={{
+              color: testResult.success
+                ? 'oklch(0.40 0.15 148)'
+                : 'var(--destructive)',
+            }}
+          >
+            {testResult.success
+              ? t('form.testSuccess')
+              : t('form.testFailed', {
+                  error: testResult.message ?? 'Unbekannter Fehler',
+                })}
+          </p>
+          {/* 401 hint for Exchange */}
+          {!testResult.success &&
+            form.protocol === 'exchange' &&
+            testResult.message?.includes('401') && (
+              <div className="rounded bg-muted/50 px-3 py-2 text-xs text-muted-foreground space-y-1">
+                <p className="font-medium">{t('form.exchangeAuthHint')}</p>
+                <ul className="list-disc list-inside space-y-0.5">
+                  <li>{t('form.exchangeAuthHint1')}</li>
+                  <li>{t('form.exchangeAuthHint2')}</li>
+                  <li>{t('form.exchangeAuthHint3')}</li>
+                  <li>{t('form.exchangeAuthHint4')}</li>
+                </ul>
+              </div>
+            )}
+        </div>
       )}
 
       {/* Inline save feedback */}