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

test/unit/main.test.js

@@ -1,4 +1,4 @@
-// Unit tests for src/main.js, run with Node's built-in test runner by the
+// Unit tests for web/src/main.js, run with Node's built-in test runner by the
 // test script in package.json. Importing the module does not start the
 // page.
 
@@ -15,7 +15,7 @@ import {
     latencyHex,
     measureLatency,
     tick,
-} from "../../src/main.js";
+} from "../../web/src/main.js";
 
 // There is no page here, so the tests stand in for it. The debug log looks
 // for its panel by id and finds none. Each element of a host's row that