refactor(housekeeping): return result from bulkImport, remove dead server calls, sync i18n

- bulkImportPermissions now returns {count, errors} instead of void
- ImportSection shows per-entry error details in toast
- Remove testRankPermission server action (test is 100% client-side)
- Clean up unused testing state in TestSection
- Sync pages.admin.{import,translations} keys to all 20 languages
- Add importedWithErrors translation key to all locales

src/messages/en.json

@@ -1876,6 +1876,7 @@
 				"emptyInput": "Empty input",
 				"invalidJson": "Invalid JSON",
 				"imported": "Imported!",
+				"importedWithErrors": "Imported {count} permissions with {errors} errors",
 				"presetApplied": "Preset applied!",
 				"cleared": "All permissions cleared!",
 				"invalidRank": "Invalid rank",