The page's script is TypeScript in web/src, built and minified with swc

- web/src/*.ts: the script that was inline in index.html and login.html, split along its
  existing sections. Still one scope, concatenated in order, not modules.
- web/build.mjs strips the types, puts the script in the page and minifies it with swc;
  build.rs runs it into OUT_DIR and web.rs include_str!s the result. 137 KB -> 106 KB.
- npx tsc -p . type-checks web/src, loosely; the handful of annotations it needed
  change no behaviour.
- The Docker build installs node and swc (npm ci --omit=dev).
- Two list requests racing no longer let the older one win, and switching tabs clears
  the selection it closes, which made a browser test flaky.

Closes #23, #24.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/login.ts

@@ -0,0 +1,15 @@
+document.getElementById('f').onsubmit = async e => {
+  e.preventDefault();
+  const msg = document.getElementById('msg');
+  msg.textContent = '';
+  const r = await fetch('/api/login', {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({
+      name: (document.getElementById('name') as HTMLInputElement).value,
+      password: (document.getElementById('pw') as HTMLInputElement).value,
+    }),
+  });
+  if (r.ok) location.href = '/';
+  else msg.textContent = await r.text() || 'Sign in failed';
+};