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

.dockerignore

@@ -72,10 +72,10 @@
 **/*.sublime-*
 
 # This repository's own entries, after the shared content above: the
-# frontend build, the viewport test's output, what `make build` and
-# `make run` in backend/ leave behind, and log files at the root.
+# frontend build, the viewport test's output, the binary `make build`
+# writes and the reports `make run` stores, and log files at the root.
 /dist
 /tmp
-/backend/netwatch-server
-/backend/data
+/netwatch-server
+/data
 /*.log