Add configuration files and update project documentation

- Introduced .editorconfig for consistent coding styles across the project.
- Added .golangci.yml for Go linting configuration.
- Updated AGENTS.md to clarify project structure and components.
- Enhanced CONTRIBUTING.md with Makefile usage for common tasks.
- Updated Dockerfiles to use Go 1.24 and improved build instructions.
- Refined README.md and deployment documentation for clarity.
- Added testing documentation in testing.md for backend and frontend tests.
- Introduced Makefile for streamlined development commands and tasks.

internal/app/topic.go

@@ -38,6 +38,7 @@ func (t *Topic[T]) Close() {
 	t.c = t.c[:0]
 }
 
+// Merge represents a map merge event (two maps becoming one).
 type Merge struct {
 	From, To int
 	Shift    Coord