feat(webui): complete postbox quick access

webui/src/features/postbox/PostboxPage.tsx

@@ -45,6 +45,7 @@ import { FormGrid,
   type ApiSettings,
   type AuthInfo
 } from "@govoplan/core-webui";
+import { useLocation, useNavigate } from "react-router";
 import {
   createPostboxGrouping,
   createPostboxMessage,
@@ -110,13 +111,16 @@ export default function PostboxPage({
   settings: ApiSettings;
   auth: AuthInfo;
 }) {
+  const location = useLocation();
+  const navigate = useNavigate();
   const requestedMessageId = useRef(
-    new URLSearchParams(window.location.search).get("message") ?? ""
+    new URLSearchParams(location.search).get("message") ?? ""
   );
   const requestedPostboxId = useRef(
-    new URLSearchParams(window.location.search).get("postbox") ?? ""
+    new URLSearchParams(location.search).get("postbox") ?? ""
   );
   const requestedMessageLoaded = useRef(false);
+  const requestedComposeLoaded = useRef(false);
   const [postboxes, setPostboxes] = useState<PostboxDirectoryItem[]>([]);
   const [groupings, setGroupings] = useState<PostboxGrouping[]>([]);
   const [selectedScope, setSelectedScope] = useState("all");
@@ -269,6 +273,44 @@ export default function PostboxPage({
     void loadDirectory();
   }, [loadDirectory]);
 
+  useEffect(() => {
+    const parameters = new URLSearchParams(location.search);
+    if (
+      requestedComposeLoaded.current ||
+      parameters.get("quickAction") !== "compose" ||
+      loadingDirectory
+    ) {
+      return;
+    }
+    requestedComposeLoaded.current = true;
+    const requestedId = parameters.get("postbox");
+    const postbox =
+      postboxes.find((item) => item.id === requestedId) ?? postboxes[0] ?? null;
+    if (canSend && postbox) {
+      setSelectedPostboxId(postbox.id);
+      openComposeFor(postbox);
+    } else if (!canSend) {
+      setError(POSTBOX_INTERFACE_I18N.noSendReason);
+    } else {
+      setError(POSTBOX_INTERFACE_I18N.noPostbox);
+    }
+
+    parameters.delete("quickAction");
+    const search = parameters.toString();
+    navigate(
+      { pathname: location.pathname, search: search ? `?${search}` : "" },
+      { replace: true, state: location.state }
+    );
+  }, [
+    canSend,
+    loadingDirectory,
+    location.pathname,
+    location.search,
+    location.state,
+    navigate,
+    postboxes
+  ]);
+
   useEffect(() => {
     void loadMessages();
   }, [loadMessages]);
@@ -469,6 +511,10 @@ export default function PostboxPage({
   function openCompose() {
     const postbox = selectedPostbox ?? postboxes[0] ?? null;
     if (!postbox) return;
+    openComposeFor(postbox);
+  }
+
+  function openComposeFor(postbox: PostboxDirectoryItem) {
     setReplyParent(null);
     const next = {
       ...emptyMessageDraft(),