Update gitignore files for all components

Root: add OS/IDE/secrets patterns
webapp: add .vite/, .tsbuildinfo, .env.local
backend: add /createuser binary, bin/, uploads/ (submodule bump)
app: remove redundant entries, add *.hprof, *.class

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

.gitignore

@@ -1 +1,13 @@
+# Environment / Secrets
 .env
+*.env
+
+# OS
+.DS_Store
+Thumbs.db
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo