Refactor comic page generation and add add-page API

Introduces a new /api/add-page endpoint for adding pages to existing comics, refactors prompt construction into a shared utility (lib/prompt.ts), and updates the editor and modal components to use the new API and prompt builder. Removes manual style and character selection in the modal, streamlining the page generation workflow and ensuring previous story context is referenced automatically.

app/editor/[storySlug]/page.tsx

@@ -22,8 +22,10 @@ interface PageData {
 
 interface StoryData {
   id: string;
+  slug: string;
   title: string;
   description?: string | null;
+  style: string;
   userId?: string | null;
 }
 
@@ -134,10 +136,8 @@ export default function StoryEditorPage() {
 
   const handleGeneratePage = async (data: {
     prompt: string;
-    style: string;
     characterFiles?: File[];
     characterUrls?: string[];
-    isContinuation?: boolean;
   }) => {
     try {
       const apiKey = localStorage.getItem("together_api_key");
@@ -146,23 +146,22 @@ export default function StoryEditorPage() {
         return;
       }
 
-      const response = await fetch("/api/generate-comic", {
+      const response = await fetch("/api/add-page", {
         method: "POST",
         headers: {
           "Content-Type": "application/json",
+          "x-api-key": apiKey,
         },
         body: JSON.stringify({
-          storyId: story?.id,
+          storyId: story?.slug,
           prompt: data.prompt,
-          apiKey,
-          style: data.style,
           characterImages: data.characterUrls || [],
         }),
       });
 
       if (!response.ok) {
         const errorData = await response.json();
-        throw new Error(errorData.error || "Failed to generate image");
+        throw new Error(errorData.error || "Failed to generate page");
       }
 
       const result = await response.json();
@@ -175,7 +174,7 @@ export default function StoryEditorPage() {
           image: result.imageUrl,
           prompt: data.prompt,
           characterUploads: data.characterUrls || [],
-          style: data.style,
+          style: story?.style || "noir",
         },
       ]);
       setCurrentPage(pages.length);
@@ -183,7 +182,7 @@ export default function StoryEditorPage() {
     } catch (error) {
       console.error("Error generating page:", error);
       toast({
-        title: "Generation failed",
+        title: "Failed to generate page",
         description:
           error instanceof Error ? error.message : "Failed to generate page",
         variant: "destructive",
@@ -242,13 +241,6 @@ export default function StoryEditorPage() {
         onClose={() => setShowGenerateModal(false)}
         onGenerate={handleGeneratePage}
         pageNumber={pages.length + 1}
-        allPages={pages.map((page, index) => ({
-          pageNumber: page.id,
-          characterImages: page.characterUploads || [],
-          prompt: page.prompt,
-          imageUrl: page.image,
-          style: page.style,
-        }))}
       />
       <PageInfoSheet
         isOpen={showInfoSheet}