feat: design system overhaul — sidebar, AI chats, settings, brainstorm, color cleanup

- Sidebar: dynamic brand-accent colors, brainstorm section restyled
- AI chat general: popup panel with expand/collapse, hides when contextual AI open
- AI chat contextual: tabs reordered (Actions first), X close button, height fix
- Settings: all tabs restyled, 6 new color presets (sage, terracotta, iron, etc.)
- Global color cleanup: emerald/orange hardcoded → brand-accent dynamic
- Brainstorm page: orange → brand-accent throughout
- PageEntry animation component added to key pages
- Floating AI button: bg-brand-accent instead of hardcoded black
- i18n: all 15 locales updated with new AI/billing keys
- Billing: freemium quota tracking, BYOK, stripe subscription scaffolding
- Admin: integrated into new design
- AGENTS.md + CLAUDE.md project rules added

memento-note/lib/ai/tools/task-extract.tool.ts

@@ -2,7 +2,7 @@ import { tool } from 'ai'
 import { z } from 'zod'
 import { toolRegistry } from './registry'
 import { prisma } from '@/lib/prisma'
-import { getTagsProvider } from '@/lib/ai/factory'
+import { withAiProviderFallback } from '@/lib/ai/fallback'
 import { getSystemConfig } from '@/lib/config'
 
 toolRegistry.register({
@@ -44,7 +44,6 @@ toolRegistry.register({
           const lang = locale === 'fr' ? 'français' : locale === 'es' ? 'espagnol' : locale === 'de' ? 'allemand' : locale === 'it' ? 'italien' : locale === 'pt' ? 'portugais' : locale === 'nl' ? 'néerlandais' : locale === 'ru' ? 'russe' : locale === 'zh' ? 'chinois' : locale === 'ja' ? 'japonais' : locale === 'ar' ? 'arabe' : locale === 'fa' ? 'persan' : locale === 'hi' ? 'hindi' : 'English'
 
           const config = await getSystemConfig()
-          const provider = getTagsProvider(config)
 
           const prompt = `You are a task extraction specialist. Analyze the following notes and extract ALL action items, tasks, and TODOs.
 
@@ -72,7 +71,9 @@ Format each task as:
 - **Deadline**: ...
 - **Status**: ...`
 
-          const result = await provider.generateText(prompt)
+          const result = await withAiProviderFallback('tags', config, (provider) =>
+            provider.generateText(prompt)
+          )
 
           const summaryTitle = locale === 'fr'
             ? `Action Items — ${new Date().toLocaleDateString('fr-FR')}`