chore: add root gitignore for local and build artifacts

.gitignore

@@ -0,0 +1,27 @@
+# Dependencies
+node_modules/
+frontend/node_modules/
+backend/vendor/
+
+# Frontend build and framework artifacts
+frontend/.svelte-kit/
+frontend/build/
+frontend/test-results/
+frontend/playwright-report/
+frontend/.vite/
+
+# Runtime data and local services
+data/postgres/
+data/redis/
+
+# Logs and local env files
+*.log
+.env
+.env.*
+*.local
+
+# OS and editor files
+.DS_Store
+Thumbs.db
+.idea/
+.vscode/