chore: remove committed root artifacts (log.txt, sqlite_leak_fix.png, default.tar.gz)

These were committed to the repo root but are build/debug byproducts:
- log.txt: empty 0-byte file
- sqlite_leak_fix.png: unreferenced 832KB image
- default.tar.gz: 1.96MB, only used as a test fixture OUTPUT (tests write it
  to a temp dir, never read from repo root)

Add ignore rules so they cannot be re-committed. Part of audit cleanup
(HA-D11-001 / HA-D3-001).

.gitignore

@@ -97,6 +97,12 @@ apps/desktop/src/**/*.d.ts
 !apps/desktop/src/plugins/*/plugin.js
 !apps/desktop/src/global.d.ts
 !apps/desktop/src/vite-env.d.ts
+
+# Repo-root build/debug artifacts that must never be committed
+log.txt
+sqlite_leak_fix.png
+*.png.bak
+default.tar.gz
 apps/shared/src/**/*.js
 apps/shared/src/**/*.js.map
 apps/shared/src/**/*.d.ts