Fix Nitro client launcher: read the nitro_path setting

The /client launcher read a non-existent `nitro_client_url` setting, so it
always fell through to "No client configured" and the client never launched.
Faithful to AtomCMS's NitroController + nitro.blade.php, build the launch URL
as {nitro_path}/index.html?sso=<ticket> plus the toolbar colour params, via a
shared buildNitroClientUrl helper. The Flash launcher's Nitro fallback used the
same dead key and is fixed too.

src/lib/services/clients.ts

@@ -0,0 +1,39 @@
+import { siteSettings } from "./site-settings";
+
+/**
+ * Builds the Nitro client launch URL, faithful to AtomCMS's NitroController +
+ * nitro.blade.php:
+ *
+ *   {nitro_path}/index.html?sso={ticket}&toolbar_primary=…&toolbar_hover=…
+ *                          &toolbar_border=…&toolbar_text=…
+ *
+ * The client files are served by the web root at `nitro_path` (e.g.
+ * `/Nitro-V3/dist`). Returns "" when no `nitro_path` is configured.
+ */
+export async function buildNitroClientUrl(ticket: string): Promise<string> {
+  const [nitroPathRaw, tPrimary, tHover, tBorder, tText, bPrimary, bHover, bBorder, bText] =
+    await Promise.all([
+      siteSettings.get("nitro_path", ""),
+      siteSettings.get("toolbar_primary_color", ""),
+      siteSettings.get("toolbar_hover_color", ""),
+      siteSettings.get("toolbar_border_color", ""),
+      siteSettings.get("toolbar_text_color", ""),
+      siteSettings.get("button_primary_color", ""),
+      siteSettings.get("button_hover_color", ""),
+      siteSettings.get("button_border_color", ""),
+      siteSettings.get("button_text_color", ""),
+    ]);
+
+  const nitroPath = (nitroPathRaw ?? "").trim().replace(/\/+$/, "");
+  if (!nitroPath) return "";
+
+  // Same fallbacks as the blade: toolbar_* color, else button_* color, else the
+  // atom defaults. URLSearchParams encodes "#" → "%23" so the query is valid.
+  const params = new URLSearchParams({ sso: ticket });
+  params.set("toolbar_primary", tPrimary || bPrimary || "#eeb425");
+  params.set("toolbar_hover", tHover || bHover || "#cf9d15");
+  params.set("toolbar_border", tBorder || bBorder || "#cf9d15");
+  params.set("toolbar_text", tText || bText || "#1a1a2e");
+
+  return `${nitroPath}/index.html?${params.toString()}`;
+}

src/lib/services/site-settings.ts

@@ -6,7 +6,7 @@ const DEFAULTS: Record<string, string> = {
   hotel_name: "Atom",
   habbo_imaging_url: "https://www.habbo.com/habbo-imaging/avatarimage",
   logo_url: "",
-  nitro_client_url: "",
+  nitro_path: "",
 };
 
 /**