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.

.gitea/workflows/ci.yml

@@ -70,30 +70,3 @@ jobs:
       - uses: actions/checkout@v4
       - name: docker build (verify image builds; no push)
         run: docker build -f compose/oikos/Dockerfile -t oikos:ci .
-
-  web:
-    runs-on: ubuntu-latest
-    defaults:
-      run:
-        working-directory: web
-    steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
-        with:
-          node-version: '22'
-          cache: npm
-          cache-dependency-path: web/package-lock.json
-      - run: npm ci
-      - name: svelte-check (advisory — baseline not yet clean)
-        run: npm run check
-        continue-on-error: true
-      - name: eslint (advisory — baseline not yet clean)
-        run: npm run lint
-        continue-on-error: true
-      - name: prettier format check (advisory — baseline not yet clean)
-        run: npm run format:check
-        continue-on-error: true
-      - name: test
-        run: npm run test
-      - name: build
-        run: npm run build