refactor(web): restructure into api/domain/services/worker; capabilities, file domains, video covers

- dissolve core-bridge into api (wire contract), domain (models), services (what the UI
  calls) and worker (everything that runs in the Web Worker, grouped by account, crypto,
  space, files, shares, runtime); regroup features, lib and store by responsibility and
  delete unused components
- the UI only reads backend capabilities (domain/capabilities); one tokenRole picks the
  token, hasCode/isRetryable handle errors; pre-checks that decided permissions on the
  client are gone; tests fail if those rules are reimplemented
- files go straight to the file domain (create, upload, download, delete, commit, cancel);
  the host sees one registration per file; creating a channel allocates a file domain and
  works even when the file service is down
- file panel shows which channel the files belong to and its space usage; unlimited files
  preview in chat; videos get a stored cover; the file service status is shown
- fix: console flooded by Retry-After reads on every upload frame

web/src/domain/settings.ts

@@ -0,0 +1,8 @@
+import type { DefaultsBody } from '@/api/generated';
+import type { CreateOptions } from './types';
+
+export function creationOptions(defaults: DefaultsBody): CreateOptions {
+  const settings = defaults.channel;
+  return { mode: defaults.channel_mode, maxMembers: settings.max_members, ttlSeconds: settings.ttl_seconds, membersCanUpload: settings.members_can_upload,
+    fileMaxDownloads: settings.file_max_downloads, joinPolicy: settings.join_policy };
+}