Fix bugs, UX rough edges, add ntfy.sh + network discovery

Bugs fixed:
- Status page: autoRefresh checkbox now actually pauses the interval
- Dashboard edit modal: hide URL field for heartbeat resources (was always shown as required)
- Dashboard: apply items_per_page, default_sort, and refresh_interval from settings on mount
- Dashboard: call loadResources() immediately on mount (was waiting 15s for fallback)
- Observability: listen for WS 'metrics' messages so tab updates live, not just on poll

UX improvements:
- Dashboard: replaced window.confirm() with inline Confirm/Cancel buttons for single and bulk delete
- Dashboard: skeleton rows shown while initial data loads (no more flash of empty state)
- Notifications: WebSocket moved from window global to useRef; exponential backoff on reconnect
- Notifications: replaced window.confirm() with inline Confirm/Cancel for Clear All
- ResourceDetail: initial API calls run in parallel via Promise.all

New features:
- ntfy.sh push notification channel: enable in Settings, enter topic, get mobile push alerts
- Network Discovery: Actions → Discover Network scans LAN for reachable hosts, probes HTTP ports, and lets you add any found host to monitoring in one click

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/build/static/js/main.f56b4907.js.LICENSE.txt

@@ -0,0 +1,101 @@
+/*! decimal.js-light v2.5.1 https://github.com/MikeMcl/decimal.js-light/LICENCE */
+
+/**
+ * @license React
+ * react-dom-client.production.js
+ *
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @license React
+ * react-dom.production.js
+ *
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @license React
+ * react-jsx-runtime.production.js
+ *
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @license React
+ * react.production.js
+ *
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @license React
+ * scheduler.production.js
+ *
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @license React
+ * use-sync-external-store-shim.production.js
+ *
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @license React
+ * use-sync-external-store-shim/with-selector.production.js
+ *
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @license React
+ * use-sync-external-store-with-selector.production.js
+ *
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * react-router v7.10.0
+ *
+ * Copyright (c) Remix Software Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE.md file in the root directory of this source tree.
+ *
+ * @license MIT
+ */
+
+/** @license React v17.0.2
+ * react-is.production.min.js
+ *
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */