Add loading state and style constants, enhance API key modal with delete

lib/constants.ts

@@ -0,0 +1,22 @@
+export const COMIC_STYLES = [
+  {
+    id: "american-modern",
+    name: "American Modern",
+    prompt: "contemporary American superhero comic style, bold vibrant colors, dynamic heroic poses, detailed muscular anatomy, cinematic action scenes, modern digital art",
+  },
+  {
+    id: "manga",
+    name: "Manga",
+    prompt: "Japanese manga style, clean precise black linework, screen tone shading, expressive eyes, dynamic speed lines, black and white with impact effects",
+  },
+  {
+    id: "noir",
+    name: "Noir",
+    prompt: "film noir style, high contrast black and white, deep dramatic shadows, 1940s detective aesthetic, heavy bold inking, moody atmospheric lighting",
+  },
+  {
+    id: "vintage",
+    name: "Vintage",
+    prompt: "Golden Age 1950s comic style, visible halftone Ben-Day dots, limited retro color palette, nostalgic warm tones, classic adventure comics",
+  },
+] as const;