caldav/carddav: officer-caldav sidecar and the /dav door

first two steps of docs/nextcloud-replacement.md — the half that has to work on
a phone, because that is the half that cannot be faked.

radicale is supervised by the sidecar rather than reimplemented. nextcloud does
not implement caldav either; it vendors sabre/dav. icalendar and vcard are a
weekend, but sync-collection, rrule expansion, vtimezone and ctag/etag are not,
and when they are subtly wrong a phone does not error — it silently stops
syncing, or silently duplicates every event.

two doors, because a browser should not speak dav:

  /dav/*        top-level, http basic against a scoped app password, every
                verb and every dav header forwarded verbatim. this is what
                davx5 and ios talk to. same reasoning as /api/vault being
                mounted outside protectedRouter.
  /api/caldav/* the ordinary sidecar proxy, for officer's own ui. json.

the shared proxy factory could not carry the dav door: it forwards three
headers and dav dies without Depth, and it derives the user from a jwt a phone
cannot hold. so it is a separate file, per that factory's own instruction never
to grow per-app logic.

new `dav_app_passwords` — a phone cannot do jwt, and the alternative is the
account password living in a phone's account manager. argon2, shown once,
revocable per device, and accepted ONLY by /dav.

.well-known/caldav and carddav redirect to the dav root. they are most of what
makes adding an account feel transparent, and they need naming explicitly in
server.tsx or the SPA `/*` fallback answers the phone with html.

verified end to end against the running stack: 401 + WWW-Authenticate
unauthenticated; 207 with calendar-access and addressbook advertised; MKCALENDAR,
PUT and GET of a real VEVENT; calendar-query and sync-collection REPORTs; MKCOL,
PUT and GET of a real vCard. X-Script-Name is set because radicale otherwise
generates hrefs at / and the client follows them into the SPA.

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

src/servers/api/dav/sync-router.ts

@@ -0,0 +1,125 @@
+import { createRouter } from '../../create-router';
+import { getUserByEmail, verifyDavAppPassword } from 'officerdb';
+import { getCaldavUrl } from './sidecar-server';
+
+// The DAV door: `/dav/*`, mounted TOP-LEVEL, outside protectedRouter.
+//
+// WHY IT IS NOT UNDER /api AND NOT BEHIND userMiddleware. DAVx5, iOS Calendar, macOS and Thunderbird
+// speak CalDAV over HTTPS with HTTP Basic auth on every single request. They cannot log into Officer,
+// cannot hold a 30-day JWT, cannot refresh one and cannot answer a passkey challenge. This is the same
+// situation `/api/vault` is in — "the Bitwarden client carries its own bearer token, not a platform
+// session JWT, so userMiddleware would 401 it" (hono.ts) — with a different credential type.
+//
+// The credential is a DAV app password (`dav_app_passwords`), scoped to this mount and nothing else.
+// An app password is NOT a session: userMiddleware must never learn to accept one, or a device that
+// syncs a calendar would also reach the wallet.
+//
+// Everything is forwarded verbatim to the caldav sidecar, which forwards it to Radicale. The platform
+// authenticates and moves bytes; it does not parse a single line of iCalendar. That restraint is the
+// same one create-proxy.ts documents, and for the same reason.
+
+export const davSyncRouter = createRouter();
+
+const unauthorized = () =>
+  new Response('Unauthorized', {
+    status: 401,
+    // Without this header a DAV client will not prompt for credentials at all — it just fails. The
+    // realm string is what the phone shows in its password dialog.
+    headers: { 'WWW-Authenticate': 'Basic realm="Officer DAV", charset="UTF-8"' },
+  });
+
+type BasicCreds = { username: string; password: string };
+
+function parseBasic(header: string | undefined): BasicCreds | null {
+  if (!header?.startsWith('Basic ')) return null;
+  let decoded: string;
+  try {
+    decoded = Buffer.from(header.slice(6), 'base64').toString('utf8');
+  } catch {
+    return null;
+  }
+  // Split on the FIRST colon only — a generated password never contains one, but an email local-part
+  // legally can, and splitting greedily would break those accounts in a way that looks like a wrong
+  // password.
+  const at = decoded.indexOf(':');
+  if (at < 0) return null;
+  return { username: decoded.slice(0, at), password: decoded.slice(at + 1) };
+}
+
+// Same list the sidecar forwards, and for the same reason: `Depth` decides whether PROPFIND returns a
+// collection, its children or the whole tree, so dropping it makes every calendar look empty.
+const REQUEST_HEADERS = [
+  'depth',
+  'content-type',
+  'content-length',
+  'if',
+  'if-match',
+  'if-none-match',
+  'destination',
+  'overwrite',
+  'lock-token',
+  'timeout',
+  'prefer',
+  'user-agent',
+] as const;
+
+const RESPONSE_HEADERS = [
+  'content-type',
+  'dav',
+  'allow',
+  'etag',
+  'last-modified',
+  'location',
+  'lock-token',
+  'preference-applied',
+  'vary',
+] as const;
+
+davSyncRouter.all('/*', async (ctx) => {
+  const creds = parseBasic(ctx.req.header('authorization'));
+  if (!creds) return unauthorized();
+
+  const user = await getUserByEmail(creds.username);
+  if (!user) return unauthorized();
+
+  const userId = await verifyDavAppPassword(user.id, creds.password);
+  if (!userId) return unauthorized();
+
+  const base = getCaldavUrl();
+  if (!base) return new Response('caldav sidecar not available', { status: 503 });
+
+  const url = new URL(ctx.req.url);
+  // The sidecar mounts DAV at /dav too, so the prefix is preserved rather than stripped — Radicale
+  // generates absolute hrefs in its multistatus responses, and if the path the client sees differs
+  // from the path the server thinks it is at, every href points somewhere that 404s.
+  const target = `${base}${url.pathname}${url.search}`;
+
+  const headers: Record<string, string> = {};
+  for (const name of REQUEST_HEADERS) {
+    const value = ctx.req.header(name);
+    if (value) headers[name] = value;
+  }
+  headers['X-Officer-User'] = String(userId);
+
+  const method = ctx.req.method;
+  const hasBody = method !== 'GET' && method !== 'HEAD';
+
+  let upstream: Response;
+  try {
+    upstream = await fetch(target, {
+      method,
+      headers,
+      body: hasBody ? await ctx.req.arrayBuffer() : undefined,
+    });
+  } catch (err) {
+    console.error('[dav] proxy fetch failed', { path: url.pathname, error: String(err) });
+    return new Response('caldav sidecar unreachable', { status: 502 });
+  }
+
+  const out = new Headers();
+  for (const name of RESPONSE_HEADERS) {
+    const value = upstream.headers.get(name);
+    if (value) out.set(name, value);
+  }
+  return new Response(upstream.body, { status: upstream.status, headers: out });
+});