Move to the layout REPO_POLICIES.md gives (closes #30)

The Go module moves from backend/ to the root (go.mod, go.sum,
.golangci.yml, cmd/, internal/), the page's source to web/, and nginx's
two files to configs/. backend/ is gone: its LICENSE and .dockerignore
are deleted, and its .gitignore entries, README and scripts are folded
into the root ones. script/build builds the server binary after the
frontend; script/run and script/clean move up from backend/script/;
make test, lint, fmt and fmt-check do what the backend's did. Vite's
root is web/ and it still builds into dist/. go.mod ignores
node_modules/, whose npm packages can ship .go files. script/bootstrap
no longer installs gcc, which only the host Go tests needed.

Model: opus-5-5

eslint.config.js

@@ -8,7 +8,7 @@ export default defineConfig([
     js.configs.recommended,
     {
         // The page, and facts.js, which the viewport test runs inside it.
-        files: ["src/**/*.js", "test/viewport/facts.js"],
+        files: ["web/src/**/*.js", "test/viewport/facts.js"],
         languageOptions: {
             globals: {
                 ...globals.browser,