fix(chart): improve error handling and color variety

- Add quotaExceeded flag to response for better error UX
- Show dedicated quota exceeded state with upgrade button
- Improve AI prompt to better detect data patterns
- Add chart type-specific colors (blue, indigo, emerald, violet, etc.)
- Replace generic primary/10 colors with varied accent colors

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

memento-note/lib/theme-script.ts

@@ -3,8 +3,9 @@
  */
 import { normalizeThemeId } from './apply-document-theme'
 
-export function getThemeScript(serverTheme: string = 'light') {
+export function getThemeScript(serverTheme: string = 'light', serverAccentColor: string | null = null) {
   const fallback = normalizeThemeId(serverTheme)
+  const defaultAccent = serverAccentColor || '#A47148'
   return `
 (function() {
   try {
@@ -28,7 +29,8 @@ export function getThemeScript(serverTheme: string = 'light') {
       if (theme === 'midnight') root.classList.add('dark');
     }
     var accentStored = localStorage.getItem('accent-color');
-    if (accentStored) root.style.setProperty('--color-brand-accent', accentStored);
+    var effectiveAccent = accentStored || ${JSON.stringify(defaultAccent)};
+    root.style.setProperty('--color-brand-accent', effectiveAccent);
   } catch (e) {
     console.error('Theme script error', e);
   }