refactor(settings): move sidebar settings into a modal

Clicking Settings now opens a dialog with the status-check interval and
canvas snap options plus Save/Cancel, replacing the inline left-panel view.
Removes the 'settings' Sidebar view and SettingsPanel component.

ha-relevant: maybe

frontend/src/App.tsx

@@ -20,6 +20,7 @@ import { LoginPage } from '@/components/LoginPage'
 import { NodeModal } from '@/components/modals/NodeModal'
 import { EdgeModal } from '@/components/modals/EdgeModal'
 import { ScanConfigModal } from '@/components/modals/ScanConfigModal'
+import { SettingsModal } from '@/components/modals/SettingsModal'
 import { ZigbeeImportModal } from '@/components/zigbee/ZigbeeImportModal'
 import { GroupRectModal, type GroupRectFormData } from '@/components/modals/GroupRectModal'
 import { TextModal, type TextFormData } from '@/components/modals/TextModal'
@@ -69,6 +70,7 @@ export default function App() {
   const [pendingConnection, setPendingConnection] = useState<Connection | null>(null)
   const [editEdgeId, setEditEdgeId] = useState<string | null>(null)
   const [scanConfigOpen, setScanConfigOpen] = useState(false)
+  const [settingsOpen, setSettingsOpen] = useState(false)
   const [exportModalOpen, setExportModalOpen] = useState(false)
   const [zigbeeImportOpen, setZigbeeImportOpen] = useState(false)
 
@@ -608,6 +610,7 @@ export default function App() {
             onScan={() => setScanConfigOpen(true)}
             onZigbeeImport={() => setZigbeeImportOpen(true)}
             onSave={handleSave}
+            onOpenSettings={() => setSettingsOpen(true)}
             forceView={sidebarForceView}
             onOpenPending={openPendingModal}
           />
@@ -805,6 +808,10 @@ export default function App() {
         />
         <ShortcutsModal open={shortcutsOpen} onClose={() => setShortcutsOpen(false)} />
 
+        {!STANDALONE && (
+          <SettingsModal open={settingsOpen} onClose={() => setSettingsOpen(false)} />
+        )}
+
         <PendingDevicesModal
           open={pendingModalOpen}
           onClose={() => setPendingModalOpen(false)}