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/data-urls/lib/parser.js

@@ -0,0 +1,69 @@
+"use strict";
+const MIMEType = require("whatwg-mimetype");
+const { parseURL, serializeURL, percentDecodeString } = require("whatwg-url");
+const { stripLeadingAndTrailingASCIIWhitespace, isomorphicDecode, forgivingBase64Decode } = require("./utils.js");
+
+module.exports = stringInput => {
+  const urlRecord = parseURL(stringInput);
+
+  if (urlRecord === null) {
+    return null;
+  }
+
+  return module.exports.fromURLRecord(urlRecord);
+};
+
+module.exports.fromURLRecord = urlRecord => {
+  if (urlRecord.scheme !== "data") {
+    return null;
+  }
+
+  const input = serializeURL(urlRecord, true).substring("data:".length);
+
+  let position = 0;
+
+  let mimeType = "";
+  while (position < input.length && input[position] !== ",") {
+    mimeType += input[position];
+    ++position;
+  }
+  mimeType = stripLeadingAndTrailingASCIIWhitespace(mimeType);
+
+  if (position === input.length) {
+    return null;
+  }
+
+  ++position;
+
+  const encodedBody = input.substring(position);
+
+  let body = percentDecodeString(encodedBody);
+
+  // Can't use /i regexp flag because it isn't restricted to ASCII.
+  const mimeTypeBase64MatchResult = /(.*); *[Bb][Aa][Ss][Ee]64$/u.exec(mimeType);
+  if (mimeTypeBase64MatchResult) {
+    const stringBody = isomorphicDecode(body);
+    body = forgivingBase64Decode(stringBody);
+
+    if (body === null) {
+      return null;
+    }
+    mimeType = mimeTypeBase64MatchResult[1];
+  }
+
+  if (mimeType.startsWith(";")) {
+    mimeType = `text/plain${mimeType}`;
+  }
+
+  let mimeTypeRecord;
+  try {
+    mimeTypeRecord = new MIMEType(mimeType);
+  } catch (e) {
+    mimeTypeRecord = new MIMEType("text/plain;charset=US-ASCII");
+  }
+
+  return {
+    mimeType: mimeTypeRecord,
+    body
+  };
+};