Add initial project structure with backend and frontend setup

- Created backend structure with Go, including main application logic and API endpoints.
- Added Docker support for both development and production environments.
- Introduced frontend using Nuxt 3 with Tailwind CSS for styling.
- Included configuration files for Docker and environment variables.
- Established basic documentation for contributing, development, and deployment processes.
- Set up .gitignore and .dockerignore files to manage ignored files in the repository.

.env.example

@@ -0,0 +1,8 @@
+# Backend (Go)
+# HNHMAP_PORT=8080
+# HNHMAP_BOOTSTRAP_PASSWORD=  # Set once for first run: login as admin with this password to create the first admin user (then unset or leave empty)
+# Grids directory (default: grids); in Docker often /map
+# HNHMAP_GRIDS=grids
+
+# Frontend (Nuxt dev) — used in docker-compose
+# NUXT_PUBLIC_API_BASE=/map/api