Initial import of LogDarioSeq baseline

Establishes version control for the personal Logseq DB fork before
starting the server-client architecture migration and domain features
described in docs/agent-guide and the approved implementation plan.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

deps/db-sync/worker/openai_app_challenge.mjs

@@ -0,0 +1,16 @@
+const OPENAI_APPS_CHALLENGE_PATH = "/.well-known/openai-apps-challenge";
+
+export function openAiAppsChallengeResponse(request, env) {
+  const url = new URL(request.url);
+  if (request.method !== "GET" || url.pathname !== OPENAI_APPS_CHALLENGE_PATH) return null;
+
+  const token = env.OPENAI_APPS_CHALLENGE;
+  if (!token) throw new Error("OPENAI_APPS_CHALLENGE is required");
+
+  return new Response(token, {
+    headers: {
+      "cache-control": "no-store",
+      "content-type": "text/plain; charset=utf-8",
+    },
+  });
+}