feat: add import preflight summaries

Inspect every manual file, folder, and drag-and-drop import before queue admission. Report exact duplicate, filename-filter, filesystem, destination, configured size-limit, and resulting job counts in the host selection dialog with live bilingual updates.

main.js

@@ -55,6 +55,7 @@ const { buildFailedUploadSummary, buildTerminalJobSnapshots } = require('./lib/u
 const { selectPublicUploadUrl } = require('./lib/upload-confirmation');
 const { createBatchMutationGate } = require('./lib/batch-mutation-gate');
 const { createUploadStartReservation } = require('./lib/upload-start-reservation');
+const { inspectImportEntries } = require('./lib/import-preflight');
 
 const _eventLoopDelay = monitorEventLoopDelay({ resolution: 10 });
 _eventLoopDelay.enable();
@@ -2247,6 +2248,32 @@ ipcMain.handle('get-file-sizes', async (_event, paths) => {
   return out;
 });
 
+ipcMain.handle('inspect-import-files', async (_event, payload) => {
+  const input = payload && typeof payload === 'object' ? payload : {};
+  const currentConfig = configStore.load();
+  return inspectImportEntries(input.entries, {
+    existingPaths: input.existingPaths,
+    filenameFilter: currentConfig.globalSettings?.filenameFilter,
+    concurrency: 8,
+    inspectPath: async filePath => {
+      let fileStat;
+      try {
+        fileStat = await fs.promises.stat(filePath);
+      } catch (error) {
+        if (error && error.code === 'ENOENT') return { exists: false };
+        return { exists: true, readable: false };
+      }
+      if (!fileStat.isFile()) return { exists: true, readable: false, size: fileStat.size };
+      try {
+        await fs.promises.access(filePath, fs.constants.R_OK);
+      } catch {
+        return { exists: true, readable: false, size: fileStat.size };
+      }
+      return { exists: true, readable: true, size: fileStat.size };
+    }
+  });
+});
+
 ipcMain.handle('start-upload', async (_event, payload) => {
   if (closeFlushRequested) return { error: 'Die Anwendung wird gerade beendet' };
   if (!settingsImportGate.canStartUpload()) return { error: 'Einstellungen werden gerade importiert' };