feat: add secure batch completion reports

Generate immutable post-cleanup summaries only after queue, history, and recovery finalization. Add bilingual accessible report UI, host and cleanup metrics, report-bound JSON and sanitized error CSV exports, renderer reload recovery, duplicate-filename-safe accounting, and public-source verification coverage.

preload.js

@@ -9,6 +9,8 @@ contextBridge.exposeInMainWorld('api', {
   pruneHistory: (retention, opts) => ipcRenderer.invoke('prune-history', { retention, dryRun: !!(opts && opts.dryRun) }),
   exportHistory: (format) => ipcRenderer.invoke('export-history', format),
   exportSessionReport: (format) => ipcRenderer.invoke('export-session-report', format),
+  getLastBatchCompletionReport: () => ipcRenderer.invoke('get-last-batch-completion-report'),
+  exportBatchCompletionReport: (reportId, format) => ipcRenderer.invoke('export-batch-completion-report', reportId, format),
   saveTextFile: (defaultName, content, filters) => ipcRenderer.invoke('save-text-file', defaultName, content, filters),
 
   // Hoster settings
@@ -118,6 +120,9 @@ contextBridge.exposeInMainWorld('api', {
   onUploadBatchDone: (callback) => {
     ipcRenderer.on('upload-batch-done', (_event, data) => callback(data));
   },
+  onUploadBatchReport: (callback) => {
+    ipcRenderer.on('upload-batch-report', (_event, data) => callback(data));
+  },
   onUploadStats: (callback) => {
     ipcRenderer.on('upload-stats', (_event, data) => callback(data));
   },
@@ -164,6 +169,7 @@ contextBridge.exposeInMainWorld('api', {
   removeAllListeners: () => {
     ipcRenderer.removeAllListeners('upload-progress');
     ipcRenderer.removeAllListeners('upload-batch-done');
+    ipcRenderer.removeAllListeners('upload-batch-report');
     ipcRenderer.removeAllListeners('upload-stats');
     ipcRenderer.removeAllListeners('app:update-available');
     ipcRenderer.removeAllListeners('app:update-progress');