feat: Phase 1 — extract the client (web SPA + desktop) to dtoro/oikos-web

Problem: the hexagonal refactor churns the backend tree for nine more
phases; the UI delivery stack (web/ SPA, cmd/desktop Wails wrapper,
compose/web image) must move to its own repo first so doc/layout
rewrites land once on a backend-only tree.

Change:
- New repo git.hubris.network/dtoro/oikos-web (v0.33.0): web/, desktop/
  (updateURL repointed to oikos-web releases), compose/, own CI (web +
  desktop jobs), own deploy script (CI-green gate, TOCTOU guard,
  version-tagged images, prune-to-3), own webhook receiver on :9798 +
  launchd unit, own compose project publishing the same 8091:80.
- Cutover executed on mac-mini in order: oikos stack's web service
  stopped+removed, oikos-web project brought up on 8091; outer Caddy
  untouched (targets the published port) — serving + Authentik flow +
  /wails 404 quirk verified post-cutover.
- Stripped from oikos: web/, cmd/desktop/, compose/web/, desktop CI
  workflow, ci.yml web job, Makefile ui/desktop/desktop-package/install
  targets, the compose web service, oikos-web from deploy.sh's fallback
  prune list; wails + go-keyring dropped from go.mod, vendor synced.
- README / CONTRIBUTING / AGENTS.md / .agents dev+operations docs now
  point at the new repo; mbse + mascot design docs carry a path note.

Risk: production SPA serving depends on the new pipeline now; rollback
is versioned-image re-up of the old web service from a pre-split
checkout (port 8091). Desktop builds installed before the split still
check dtoro/oikos releases — one manual reinstall, noted in the
oikos-web release notes.

Verification: go vet, make test (race), make generate-check, golangci
(no new findings; baseline down 400→365); post-cutover curls —
localhost:8091 200, /wails/runtime.js 404, outer Caddy 302 Authentik.

web/node_modules/path-exists/readme.md

@@ -0,0 +1,52 @@
+# path-exists [![Build Status](https://travis-ci.org/sindresorhus/path-exists.svg?branch=master)](https://travis-ci.org/sindresorhus/path-exists)
+
+> Check if a path exists
+
+NOTE: `fs.existsSync` has been un-deprecated in Node.js since 6.8.0. If you only need to check synchronously, this module is not needed.
+
+While [`fs.exists()`](https://nodejs.org/api/fs.html#fs_fs_exists_path_callback) is being [deprecated](https://github.com/iojs/io.js/issues/103), there's still a genuine use-case of being able to check if a path exists for other purposes than doing IO with it.
+
+Never use this before handling a file though:
+
+> In particular, checking if a file exists before opening it is an anti-pattern that leaves you vulnerable to race conditions: another process may remove the file between the calls to `fs.exists()` and `fs.open()`. Just open the file and handle the error when it's not there.
+
+
+## Install
+
+```
+$ npm install path-exists
+```
+
+
+## Usage
+
+```js
+// foo.js
+const pathExists = require('path-exists');
+
+(async () => {
+	console.log(await pathExists('foo.js'));
+	//=> true
+})();
+```
+
+
+## API
+
+### pathExists(path)
+
+Returns a `Promise<boolean>` of whether the path exists.
+
+### pathExists.sync(path)
+
+Returns a `boolean` of whether the path exists.
+
+
+## Related
+
+- [path-exists-cli](https://github.com/sindresorhus/path-exists-cli) - CLI for this module
+
+
+## License
+
+MIT © [Sindre Sorhus](https://sindresorhus.com)