Redesign the library UI and add scenario cover art

Rework the home page into a single landing surface and give the app a
consistent visual language, chosen as "illuminated tome" over two other
pitched directions because it builds on the existing Cinzel + gold identity
instead of replacing it.

Home is now Continue (up to 4 in-progress stories, each showing where you
left off) over a scenario shelf, each section with a "See all" link. The
full adventure list moves to /adventures.

Scenario cover art has three tiers, in precedence order: an uploaded picture
(downscaled client-side to 400px WebP before storing), an emoji, or gradient
art generated from a hash of the title so no card is ever an empty box.
Adventures inherit their scenario's art. Images live in the row rather than
on disk because Render's free tier has no persistent volume, and it keeps
export bundles self-contained; list responses carry a cacheable
/api/scenarios/{id}/image URL rather than the base64.

Also: ambient drifting motes behind the app, loading skeletons, staggered
card entrance, ornamental scene breaks and a drop cap in the story, a
"Weaving" thinking indicator, and a toast system replacing every alert().

Two fixes found along the way:

- Importing a scenario bundle with no "tags" key returned a 500. Column
  defaults are not applied until flush, so the attribute was still None
  when the width clamp sliced it.
- Anything meaning "the story's latest narration" was missing action type
  "start", which is the only text a freshly created adventure has, so new
  adventures looked empty. Collected as NARRATION_TYPES.

Migrations 30 and 31 add scenarios.image and scenarios.icon; both are
additive with a '' default and were verified against a database stamped at
29. vite.config.js now reads AIDND_API_PORT so the recurring port-8000
clash with another local app needs no file edit.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014FGY1yvzSeKgTtRfeVtDmx

frontend/vite.config.js

@@ -1,12 +1,18 @@
 import { defineConfig } from 'vite'
 import react from '@vitejs/plugin-react'
 
+// The backend port. Overridable because 8000 is a popular default and another
+// local app squatting it silently shadows this API (its SPA catch-all answers
+// GET /api/* with index.html), which looks like an empty database rather than
+// a proxy problem. Start the backend elsewhere and set AIDND_API_PORT to match.
+const apiPort = process.env.AIDND_API_PORT || '8000'
+
 // https://vite.dev/config/
 export default defineConfig({
   plugins: [react()],
   server: {
     proxy: {
-      '/api': 'http://localhost:8000',
+      '/api': `http://localhost:${apiPort}`,
     },
   },
 })