feat(captive-portal): migrate all LocalToHub WS commands to HTTP REST

All frontend→firmware commands now use HTTP endpoints. The WebSocket
channel in the captive portal is now receive-only (firmware→frontend push):
- WiFi network save (POST /api/wifi/networks)
- WiFi network connect (POST /api/wifi/connect)
- WiFi network disconnect (POST /api/wifi/disconnect)
- OTA config endpoints (PUT /api/ota/*)
- OTA check for updates (POST /api/ota/check)

LocalToHubMessage FlatBuffers union is now empty — schema cleanup
documented in FLATBUFFERS_CHANGES.md.

Co-Authored-By: Copilot <223556219+Copilot@users.noreply.github.com>

Author: hhvrc

frontend/src/App.svelte

@@ -22,11 +22,13 @@
   import AdvancedView from '$lib/components/AdvancedView.svelte';
   import { hubState, initializeDarkModeStore, ViewModeStore } from '$lib/stores';
   import { closePortal } from '$lib/portalClose';
+  import { fetchBoardInfo } from '$lib/api';
   import { Button } from '$lib/components/ui/button';
   import { onMount } from 'svelte';
 
   onMount(() => {
     initializeDarkModeStore();
+    fetchBoardInfo();
     WebSocketClient.Instance.Connect();
   });
 

frontend/src/lib/MessageHandlers/index.ts

@@ -26,7 +26,6 @@ PayloadHandlers[HubToLocalMessagePayload.ReadyMessage] = (cli, msg) => {
   const payload = new ReadyMessage();
   msg.payload(payload);
 
-  hubState.hasPredefinedPins = payload.poggies();
   hubState.wifiConnectedBSSID = payload.connectedWifi()?.bssid() || null;
   hubState.accountLinked = payload.accountLinked();
   hubState.config = mapConfig(payload.config());