rename setup → settings throughout; persist arr creds even on test failure

Two cleanups:

1. Rename the page from 'Setup' to 'Settings' all the way down. The H1
   already said Settings; the file/component/api path were lying.
   - src/features/setup/ → src/features/settings/
   - SetupPage.tsx → SettingsPage.tsx, SetupPage → SettingsPage,
     SetupData → SettingsData, setupCache → settingsCache
   - server/api/setup.ts → server/api/settings.ts
   - /api/setup → /api/settings (only consumer is our frontend)
   - server/index.tsx import + route mount renamed
   - ScanPage's local setupChecked → configChecked

2. Sonarr (and Radarr) save flow: persist the values BEFORE running the
   connection test. The previous code returned early if the test failed,
   silently dropping what the user typed — explained the user's report
   that Sonarr 'forgets' the input. Now setConfig fires unconditionally
   on a valid (non-empty) URL+key; the test result is returned as
   { ok, saved, testError } so the UI can show 'Saved & connected' on
   success or '⚠ Saved, but connection test failed: …' on failure
   instead of erasing the input.

Note: setup_complete config key kept as-is — it represents 'has the user
configured Jellyfin' which is conceptually setup and not user-visible.

server/api/settings.ts

@@ -37,6 +37,10 @@ app.post("/jellyfin", async (c) => {
 	return c.json({ ok: true });
 });
 
+// Persist values BEFORE testing the connection. The previous behaviour
+// silently dropped what the user typed when the test failed (e.g. Sonarr
+// not yet reachable), making the field appear to "forget" the input on
+// reload. Save first, surface the test result as a warning the UI can show.
 app.post("/radarr", async (c) => {
 	const body = await c.req.json<{ url?: string; api_key?: string }>();
 	const url = body.url?.replace(/\/$/, "");
@@ -47,14 +51,12 @@ app.post("/radarr", async (c) => {
 		return c.json({ ok: false, error: "URL and API key are required" }, 400);
 	}
 
-	const result = await testRadarr({ url, apiKey });
-	if (!result.ok) return c.json({ ok: false, error: result.error });
-
 	setConfig("radarr_url", url);
 	setConfig("radarr_api_key", apiKey);
 	setConfig("radarr_enabled", "1");
 
-	return c.json({ ok: true });
+	const result = await testRadarr({ url, apiKey });
+	return c.json({ ok: result.ok, saved: true, testError: result.ok ? undefined : result.error });
 });
 
 app.post("/sonarr", async (c) => {
@@ -67,14 +69,12 @@ app.post("/sonarr", async (c) => {
 		return c.json({ ok: false, error: "URL and API key are required" }, 400);
 	}
 
-	const result = await testSonarr({ url, apiKey });
-	if (!result.ok) return c.json({ ok: false, error: result.error });
-
 	setConfig("sonarr_url", url);
 	setConfig("sonarr_api_key", apiKey);
 	setConfig("sonarr_enabled", "1");
 
-	return c.json({ ok: true });
+	const result = await testSonarr({ url, apiKey });
+	return c.json({ ok: result.ok, saved: true, testError: result.ok ? undefined : result.error });
 });
 
 app.post("/subtitle-languages", async (c) => {