fix: reset service editor on switch + add service-page settings shortcut

Settings.tsx: ServiceConfigEditor derived editable state (name, config,
secrets) from the instance prop via useState, but the parent rendered it
without a key. Switching services in the rail reused the same component, so
name/config stayed pinned to the previously selected service while
instance.id/service_type (read live from props) pointed at the new one —
saving then wrote the stale values onto the wrong row (e.g. saving qBittorrent
renamed it "Jellyfin" with Jellyfin's URL). Add key={selectedService.id} so
the editor remounts and resets on switch.

ServicePage: add a Settings shortcut in the header that deep-links to
/settings?tab=services&service=<id>. Settings now reads tab + service query
params (useSearchParams) to open the Services tab with that service
pre-selected, via a new initialServiceId prop on ServicesAdminCard.

Tests: new Settings.services.test.tsx regression test (fails without the key,
passes with it); wrap existing Settings tests in MemoryRouter since Settings
now uses useSearchParams. 166/166 frontend tests pass; typecheck + ESLint clean.

frontend/src/pages/ServicePage.tsx

@@ -1,7 +1,9 @@
 import { useMemo } from "react";
 import { useParams, useNavigate } from "react-router-dom";
+import { Settings as SettingsIcon } from "lucide-react";
 import { Alert, AlertDescription } from "@/components/ui/alert";
 import { Badge } from "@/components/ui/badge";
+import { Button } from "@/components/ui/button";
 import { Tabs, TabsContent, TabsList, TabsTrigger } from "@/components/ui/tabs";
 import { useServiceInstances } from "../hooks/useServices";
 import type { ServiceInstance } from "../types";
@@ -89,7 +91,21 @@ export function ServicePage() {
 					<h2 className="text-xl font-semibold">{instance.name}</h2>
 					<p className="text-sm text-muted-foreground">{binding.description}</p>
 				</div>
-				<Badge variant="outline">{binding.name}</Badge>
+				<div className="flex items-center gap-2">
+					<Badge variant="outline">{binding.name}</Badge>
+					<Button
+						variant="outline"
+						size="sm"
+						onClick={() =>
+							navigate(
+								`/settings?tab=services&service=${encodeURIComponent(instance.id)}`,
+							)
+						}
+					>
+						<SettingsIcon className="mr-1 h-3 w-3" />
+						Settings
+					</Button>
+				</div>
 			</div>
 
 			{/* Instance tabs (only when >1 enabled sibling) */}