nginx gets a configuration instead of the stock one

`nginx:alpine` ships a config that serves the directory and does nothing else: no compression, and no
cache headers at all. Every asset on the live site carried a TTL of zero, so a returning visitor
re-downloaded all of it — 1.1 MB by Lighthouse's count.

Written out on every start rather than kept as a file somebody edits, so what nginx does is decided in
this file and cannot drift from it.

Three lifetimes, because there are three kinds of file. `derived/` renditions are rebuilt IN PLACE —
av-club replaces the contents of `1280.webp` rather than writing a new name — so they cannot be
`immutable` however much they look like they could be, or a re-crop stays invisible for a year to
everyone who saw the old one. Bundled assets change only when a build runs, and a build changes the
HTML that names them: a week. HTML revalidates every time, because anything longer makes a publish
invisible to whoever already visited, which is the one failure that makes the whole panel look broken.

`^~` on the prefix locations. A regex location beats a prefix location in nginx, so the extension rule
would otherwise capture /derived/…/1280.webp and give it the wrong lifetime.

Validated with `nginx -t` in the real image rather than by reading it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

api/static-site.ts

@@ -1,4 +1,4 @@
-import { stat, readdir } from 'node:fs/promises';
+import { stat, readdir, writeFile } from 'node:fs/promises';
 import { join } from 'node:path';
 import { db } from 'officerdb/db';
 import { fofosAdminSettings } from '../db/schema';
@@ -181,6 +181,73 @@ export async function buildSite(secrets: {
  * the shared network by name, and a port on the host would be the site available unauthenticated beside
  * the proxy that exists to gate it.
  */
+/**
+ * The nginx configuration the container runs.
+ *
+ * Written out on every start rather than kept as a file somebody edits, so what nginx does is decided
+ * here and cannot drift. The stock `nginx:alpine` config serves the directory and nothing else: no
+ * compression, and no cache headers at all, so every asset carried a TTL of zero and a returning
+ * visitor re-downloaded the whole site.
+ *
+ * ── Three lifetimes, because there are three kinds of file ──
+ *
+ * `derived/` renditions are rebuilt IN PLACE — av-club replaces the contents of `1280.webp` rather
+ * than writing a new name. So they cannot be `immutable`, however much they look like they could be:
+ * a re-crop would be invisible to everyone who had seen the old one, for as long as the header said.
+ * Thirty days is the compromise, and it is the reason this is spelled out rather than copied from the
+ * usual recipe.
+ *
+ * Bundled assets — the stylesheet, the scripts, the fonts — change only when a build runs, and a build
+ * is also the only thing that changes the HTML that references them. A week, revalidated after.
+ *
+ * HTML is `no-cache`: revalidate every time. Not `no-store` — the file is still cached, it is just
+ * never used without asking. Anything longer and a publish is invisible to whoever already visited,
+ * which is the one failure that makes the whole panel look broken.
+ *
+ * ── Why `^~` on the prefixes ──
+ *
+ * A regex location beats a prefix location in nginx, so the extension rule below would otherwise
+ * capture `/derived/…/1280.webp` and hand it the wrong lifetime. `^~` stops the regex from being
+ * considered at all. This is the kind of thing that is correct or silently wrong with no middle.
+ */
+const NGINX_CONF = `server {
+  listen 80;
+  listen [::]:80;
+  server_name _;
+
+  root /usr/share/nginx/html;
+  index index.html;
+
+  # Text compresses; the images and video here are already compressed formats and would only burn CPU.
+  gzip on;
+  gzip_vary on;
+  gzip_min_length 1024;
+  gzip_types text/css text/plain application/javascript application/json image/svg+xml;
+
+  # Rebuilt in place by av-club, so a long life would pin a stale crop. See the note above.
+  location ^~ /derived/ {
+    expires 30d;
+    add_header Cache-Control "public";
+  }
+
+  location ^~ /media/ {
+    expires 30d;
+    add_header Cache-Control "public";
+  }
+
+  location ~* \\.(css|js|woff2|webp|png|jpg|jpeg|gif|svg|ico|mp4)$ {
+    expires 7d;
+    add_header Cache-Control "public";
+  }
+
+  location / {
+    # The build writes about/index.html, so a directory match is what serves /about.
+    try_files $uri $uri/ =404;
+    add_header Cache-Control "no-cache";
+  }
+}
+`;
+
 export async function startStatic(): Promise<{ ok: boolean; output: string }> {
   const row = await readRow();
   if (!row?.rootPath) throw new Error('No root location is set.');
@@ -188,6 +255,10 @@ export async function startStatic(): Promise<{ ok: boolean; output: string }> {
   const dist = distPath(row.rootPath);
   if (!(await stat(dist).catch(() => null))) throw new Error('There is no dist directory yet — build first.');
 
+  // Beside the site rather than inside dist/, which the build empties and replaces.
+  const conf = join(row.rootPath, 'nginx.conf');
+  await writeFile(conf, NGINX_CONF);
+
   // Expected to fail the first time; the usual case is that it was never there.
   await run([DOCKER, 'rm', '-f', CONTAINER], 30_000);
 
@@ -199,6 +270,7 @@ export async function startStatic(): Promise<{ ok: boolean; output: string }> {
       '--network', NETWORK,
       // Read-only: nginx serves this and has no business writing to somebody's build output.
       '-v', `${dist}:/usr/share/nginx/html:ro`,
+      '-v', `${conf}:/etc/nginx/conf.d/default.conf:ro`,
       IMAGE,
     ],
     120_000,