refactor: organize features and standardize frontend tooling

Colocate feature views, components, stores, and upload logic; centralize shared map utilities without changing API behavior.

Add ESLint, Prettier, EditorConfig, and VS Code settings; standardize four-space indentation and document the project structure and checks.

Validation: npm run check, npm run build, and git diff --check.

.editorconfig

@@ -0,0 +1,12 @@
+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+indent_size = 4
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.md]
+trim_trailing_whitespace = false