Docker tab: own config file, folder.view3 becomes optional sync target

- Primary store moved to /boot/config/plugins/varaverk/docker_folders.json
- No dependency on folder.view3 plugin being installed
- Auto-imports folder.view3 JSON on first run if it exists (one-time bootstrap)
- Mirrors writes to folder.view3 JSON only if that plugin's directory is present
- Toolbar shows '⇄ folder.view3' badge when sync is active

Plugin/unraid/pages/docker.php

@@ -46,6 +46,7 @@
   <button class="vv-dk-btn warn" id="vv-dk-sync-c2j" title="Apply conf desired state to folder.view3 JSON">Sync conf → JSON</button>
   <button class="vv-dk-btn prim" id="vv-dk-sync-j2c" title="Capture current JSON state back to conf">Sync JSON → conf</button>
   <button class="vv-dk-btn" id="vv-dk-edit-toggle">Edit folders</button>
+  <span style="font-size:10px;color:#2a4a2a;" id="vv-dk-fv3"></span>
   <span class="vv-dk-ts" id="vv-dk-ts"></span>
 </div>
 
@@ -159,6 +160,9 @@ function _render(data) {
   const ts = data.ts ? new Date(data.ts * 1000).toLocaleString([], {month:'numeric',day:'numeric',year:'numeric',hour:'2-digit',minute:'2-digit',second:'2-digit'}) : '';
   document.getElementById('vv-dk-ts').textContent = ts ? 'Updated: ' + ts : '';
 
+  const fv3El = document.getElementById('vv-dk-fv3');
+  if (fv3El) fv3El.textContent = data.fv3_synced ? '⇄ folder.view3' : '';
+
   _bindEvents();
 }