feat(deploy): drop the IaC layer, and make both apps runnable as containers

Moving the issuer's state into Postgres removed the last thing that tied
either app to one hosting provider. What was left was a deployment tool
describing resources that no longer existed — so this replaces it with
`wrangler`, which is what actually deploys a Worker, and adds a second way
to run each app that involves no provider at all.

Each app now has a `wrangler.jsonc` with an environment per stage, and a
`Dockerfile` beside it. The handler is the same one in both cases; what
differs is only where its settings come from. Two of them gained a second
spelling so that nothing has to branch on the runtime: Postgres arrives as
a pooled binding or as `DATABASE_URL`, and the route to the issuer is a
service binding or `AUTH_INTERNAL_URL`.

That last one is new, and it is a split the binding was already making
without saying so. `AUTH_ISSUER_URL` has to be the issuer's public name,
because it is compared literally against every token's `iss` claim — but
the public name is often not routable from inside a deployment. So the
name and the route are two settings now rather than one that cannot be
both.

DNS moves out of code and into `docs/dns.md`, which lists every hostname
and what it is for. Six records that change roughly never did not need a
tool, and the table outlives whatever is answering the names — which is
the point, since some of them will stop being Workers. The sandbox
hostnames are hyphenated rather than nested for the same reason: a
certificate covering `*.nestri.io` covers one label and not two, so
`api-sandbox.nestri.io` can become an ordinary origin later without a
certificate having to be ordered for it first.

Also drops `EMAIL_DEV_LOG` from committed configuration into `.dev.vars`,
which `wrangler deploy` cannot upload. Printing a live sign-in code to a
log should not be one forgotten override away from production.

apps/api/app/server.ts

@@ -0,0 +1,40 @@
+/**
+ * The API as an ordinary HTTP server.
+ *
+ * `index.ts` exports a handler taking `(request, env)` — the shape a Worker is
+ * invoked with, and also the shape of a plain function from a request to a
+ * response. So there is nothing here but the loop that calls it: the process
+ * environment stands in for the bindings, and a port stands in for the route.
+ *
+ * With no `AUTH` binding in that environment the middleware reaches the issuer
+ * over plain HTTP at `AUTH_ISSUER_URL`, which is a setting this deployment has
+ * either way. Nothing else differs.
+ */
+import handler, { type ApiEnv } from './index.js';
+
+const port = Number(process.env.PORT ?? 3000);
+
+Bun.serve({
+	port,
+	hostname: '0.0.0.0',
+	// A Worker runtime hands the handler a context whose `waitUntil` keeps the
+	// invocation alive past the response. A process does not need convincing to
+	// stay alive, so the equivalent is to let the promise run — with a catch,
+	// because an unobserved rejection here would take the server down rather
+	// than the request that caused it.
+	fetch: (request) =>
+		handler.fetch(
+			request,
+			process.env as unknown as ApiEnv,
+			{
+				waitUntil: (promise: Promise<unknown>) => {
+					void Promise.resolve(promise).catch((error: unknown) => {
+						console.error('[api] background task failed:', error);
+					});
+				},
+				passThroughOnException: () => {}
+			} as unknown as ExecutionContext
+		)
+});
+
+console.log(`[api] listening on http://0.0.0.0:${port}`);