feat: add theme

app/Http/Controllers/ThemeController.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Models\Theme;
+use Illuminate\Http\Request;
+
+class ThemeController extends Controller
+{
+    // List themes (for the scene theme picker and the app).
+    public function index(Request $request)
+    {
+        $query = Theme::query();
+
+        if (!$request->boolean('include_inactive')) {
+            $query->where('is_active', true);
+        }
+
+        return response()->json($query->orderBy('order')->get());
+    }
+
+    public function show($id)
+    {
+        return response()->json(Theme::findOrFail($id));
+    }
+}