docs: add features.md, restructure docs, simplify README as marketing page

.github/copilot-instructions.md

@@ -37,6 +37,10 @@
 - The root `Dockerfile` builds the Go binary and the React static assets (multi-stage build).
 - Branch from `feature/**` and target `development`.
 
+## Documentation
+- **Feature Documentation**: When adding new features, update `docs/features.md` to include the new capability. This is the canonical list of all features shown to users.
+- **README**: The main `README.md` is a marketing/welcome page. Keep it brief with top features, quick start, and links to docs. All detailed documentation belongs in `docs/`.
+
 ## CI/CD & Commit Conventions
 - **Docker Builds**: The `docker-publish` workflow skips builds for commits starting with `chore:`.
 - **Triggering Builds**: To ensure a new Docker image is built (e.g., for testing on VPS), use `feat:`, `fix:`, or `perf:` prefixes.