chore: Add .gitignore and .env.example

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

.gitignore

@@ -0,0 +1,33 @@
+# Environment
+.env
+.env.local
+
+# Rust
+backend/target/
+**/*.rs.bk
+
+# Node / Frontend
+frontend/node_modules/
+frontend/dist/
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Docker volumes (local dev)
+docker/pg_data/
+docker/nats_data/
+
+# Maps and backups (runtime data)
+maps/
+backups/
+
+# Logs
+*.log