Release v1.4.17 with security fixes, stability hardening and retry improvements

- Fix ZIP path traversal vulnerability (reject entries escaping target dir)
- Add single instance lock (prevent data corruption from multiple instances)
- Add unhandled exception/rejection handlers (prevent silent crashes)
- Fix mainWindow reference cleanup on close
- Add second-instance handler to focus existing window
- Fix claimTargetPath infinite loop (add 10k iteration bound)
- Add duplicate startItem guard (prevent concurrent downloads of same item)
- Clone session in getSnapshot to prevent live-reference mutation bugs
- Clear stateEmitTimer on clearAll to prevent dangling timer emissions
- Add extraction timeout safety (4h deadline with logging)
- Add dedicated unrestrict retry system with longer backoff for Mega-Debrid errors
- Add log rotation (10MB max, keeps one .old backup)
- Fix writeExtractResumeState missing mkdir (prevents crash on deleted dirs)
- Fix saveSessionAsync EXDEV cross-device rename with copy fallback

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

src/main/main.ts

@@ -6,6 +6,20 @@ import { IPC_CHANNELS } from "../shared/ipc";
 import { logger } from "./logger";
 import { APP_NAME } from "./constants";
 
+/* ── Single Instance Lock ───────────────────────────────────────── */
+const gotLock = app.requestSingleInstanceLock();
+if (!gotLock) {
+  app.quit();
+}
+
+/* ── Unhandled error protection ─────────────────────────────────── */
+process.on("uncaughtException", (error) => {
+  logger.error(`Uncaught Exception: ${String(error?.stack || error)}`);
+});
+process.on("unhandledRejection", (reason) => {
+  logger.error(`Unhandled Rejection: ${String(reason)}`);
+});
+
 let mainWindow: BrowserWindow | null = null;
 let tray: Tray | null = null;
 let clipboardTimer: ReturnType<typeof setInterval> | null = null;
@@ -202,6 +216,16 @@ function registerIpcHandlers(): void {
   };
 }
 
+app.on("second-instance", () => {
+  if (mainWindow) {
+    if (mainWindow.isMinimized()) {
+      mainWindow.restore();
+    }
+    mainWindow.show();
+    mainWindow.focus();
+  }
+});
+
 app.whenReady().then(() => {
   registerIpcHandlers();
   mainWindow = createWindow();
@@ -216,6 +240,10 @@ app.whenReady().then(() => {
     }
   });
 
+  mainWindow.on("closed", () => {
+    mainWindow = null;
+  });
+
   app.on("activate", () => {
     if (BrowserWindow.getAllWindows().length === 0) {
       mainWindow = createWindow();