Comprehensive bugfix release v1.6.45

Fix ~70 issues across the entire codebase including security fixes,
error handling improvements, test stabilization, and code quality.

- Fix TLS race condition with reference-counted acquire/release
- Bind debug server to 127.0.0.1 instead of 0.0.0.0
- Add overall timeout to MegaWebFallback
- Stream update installer to disk instead of RAM buffering
- Add path traversal protection in JVM extractor
- Cache DdownloadClient with credential-based invalidation
- Add .catch() to all fire-and-forget IPC calls
- Wrap app startup, clipboard, session-log in try/catch
- Add timeouts to container.ts fetch calls
- Fix variable shadowing, tsconfig path, line endings
- Stabilize tests with proper cleanup and timing tolerance
- Fix installer privileges, scripts, and afterPack null checks
- Delete obsolete _upload_release.mjs

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

tests/self-check.ts

@@ -153,7 +153,7 @@ async function main(): Promise<void> {
       createStoragePaths(path.join(tempRoot, "state-pause"))
     );
     manager2.addPackages([{ name: "pause", links: ["https://dummy/slow"] }]);
-    manager2.start();
+    await manager2.start();
     await new Promise((resolve) => setTimeout(resolve, 120));
     const paused = manager2.togglePause();
     assert(paused, "Pause konnte nicht aktiviert werden");