Build the Settings module: notification channels, event toggles, DNS badge colors

The Settings page was a "coming soon" placeholder. Port Sloth Manager's
settings feature set: Gotify/ntfy/SMTP/webhook notification channels
(each with its own test-send button), per-event toggles (DNS record
added/updated/deleted, a daily secret-expiry digest with configurable
time/timezone), and per-provider DNS badge color customization.

Settings persist in the existing `settings` key/value table via a new
settingsStore service; a notify service fans a message out to every
enabled channel. DNS record add/update/delete now fire notifications,
and a node-schedule job re-arms itself whenever the notification
settings change. Removed the now-superseded GOTIFY_URL/GOTIFY_TOKEN
env vars in favor of in-app configuration.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/pages/Dns.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from "react";
+import { useEffect, useState, type CSSProperties } from "react";
 import {
   api,
   type CurrentUser,
@@ -21,6 +21,12 @@ const PROVIDER_LABELS: Record<DnsProviderType, string> = {
 
 const emptyRecordForm: DnsRecordInput = { type: "A", name: "", content: "", ttl: 3600, priority: undefined, proxied: undefined };
 
+function providerBadgeStyle(colors: Record<string, string>, providerType: DnsProviderType): CSSProperties {
+  const color = colors[providerType];
+  if (!color) return {};
+  return { backgroundColor: `${color}22`, color, border: `1px solid ${color}55` };
+}
+
 export default function Dns({ user }: { user: CurrentUser }) {
   const isAdmin = user.role === "admin";
   const canEdit = user.role === "admin" || user.role === "operator";
@@ -29,6 +35,11 @@ export default function Dns({ user }: { user: CurrentUser }) {
   const [managingProviders, setManagingProviders] = useState(false);
   const [selectedProviderId, setSelectedProviderId] = useState<number | null>(null);
   const [error, setError] = useState<string | null>(null);
+  const [providerColors, setProviderColors] = useState<Record<string, string>>({});
+
+  useEffect(() => {
+    api.settings.providerColors().then((res) => setProviderColors(res.providerColors)).catch(() => {});
+  }, []);
 
   const [zones, setZones] = useState<DnsZone[] | null>(null);
   const [zonesError, setZonesError] = useState<string | null>(null);
@@ -212,7 +223,11 @@ export default function Dns({ user }: { user: CurrentUser }) {
                   {providers?.map((p) => (
                     <tr key={p.id}>
                       <td>{p.name}</td>
-                      <td>{PROVIDER_LABELS[p.providerType]}</td>
+                      <td>
+                        <span className="badge" style={providerBadgeStyle(providerColors, p.providerType)}>
+                          {PROVIDER_LABELS[p.providerType]}
+                        </span>
+                      </td>
                       <td>
                         <button
                           className={`badge ${p.enabled ? "bg-green-lt text-green" : "bg-secondary-lt text-secondary"} border-0`}