Add Docker Development section to CLAUDE.md

Document how to use Docker Compose when Go is not available locally.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: vojtabiberle

CLAUDE.md

@@ -49,6 +49,19 @@ APIs are designed using Goa DSL in `/api/` directory. After modifying the design
 - Run `task generate-<service>-api` to regenerate server code, OpenAPI specs, and types
 - Never hand-edit generated code
 
+## Docker Development
+
+If Go is not available locally, use Docker Compose to run all commands:
+
+```bash
+# Start a shell in the dev container
+docker-compose run --rm -u "$UID:$GID" --service-ports dev bash
+
+# Then run commands inside the container
+task lint
+task tests
+```
+
 ## Common Development Commands
 
 ### Building (Local Development)