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/postcss/lib/warning.js

@@ -0,0 +1,47 @@
+'use strict'
+
+let Container = require('./container')
+let { my } = require('./symbols')
+
+class Warning {
+  constructor(text, opts = {}) {
+    this.type = 'warning'
+    this.text = text
+
+    if (opts.node && opts.node.source) {
+      if (!opts.node[my]) {
+        // The node comes from another PostCSS copy in node_modules, so it does
+        // not have this copy’s methods. Container#normalize() rebuilds such
+        // nodes on insert, but a node passed straight to Result#warn() never
+        // goes through it.
+        Container.rebuild(opts.node)
+      }
+      let range = opts.node.rangeBy(opts)
+      this.line = range.start.line
+      this.column = range.start.column
+      this.endLine = range.end.line
+      this.endColumn = range.end.column
+    }
+
+    for (let opt in opts) this[opt] = opts[opt]
+  }
+
+  toString() {
+    if (this.node) {
+      return this.node.error(this.text, {
+        index: this.index,
+        plugin: this.plugin,
+        word: this.word
+      }).message
+    }
+
+    if (this.plugin) {
+      return this.plugin + ': ' + this.text
+    }
+
+    return this.text
+  }
+}
+
+module.exports = Warning
+Warning.default = Warning