Add first-run setup screen when required services aren't configured

When Radarr, Sonarr, or Overseerr is missing a URL or API key, the
stats API now returns 428 and the dashboard renders a full-page
setup form instead of the empty shell + fetch-error UI. The form
reuses the existing service/discord inputs (extracted out of the
settings modal so both can share them), and the background poller
skips silently until setup is complete.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/lib/settings.ts

@@ -71,6 +71,12 @@ export function getSettings(): AppSettings {
   };
 }
 
+/** Returns true iff the three services required for the dashboard to function (Radarr, Sonarr, Overseerr/Jellyseerr) have both a URL and API key. */
+export function isConfigured(s: AppSettings = getSettings()): boolean {
+  const filled = (c: ServiceConfig) => c.url.trim() !== "" && c.apiKey.trim() !== "";
+  return filled(s.radarr) && filled(s.sonarr) && filled(s.seerr);
+}
+
 /** Saves the provided settings to disk and returns the merged result. */
 export function saveSettings(settings: AppSettings): AppSettings {
   if (!existsSync(DATA_DIR)) mkdirSync(DATA_DIR, { recursive: true });