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/services/embedding.service.ts

@@ -4,7 +4,7 @@
  * Stores embeddings as native pgvector in PostgreSQL.
  */
 
-import { getAIProvider } from '../factory'
+import { withAiProviderFallback } from '../fallback'
 import { getSystemConfig } from '@/lib/config'
 
 export interface EmbeddingResult {
@@ -23,8 +23,9 @@ export class EmbeddingService {
 
     try {
       const config = await getSystemConfig()
-      const provider = getAIProvider(config)
-      const embedding = await provider.getEmbeddings(text)
+      const embedding = await withAiProviderFallback('embedding', config, (provider) =>
+        provider.getEmbeddings(text)
+      )
 
       return {
         embedding,
@@ -45,9 +46,8 @@ export class EmbeddingService {
 
     try {
       const config = await getSystemConfig()
-      const provider = getAIProvider(config)
-      const embeddings = await Promise.all(
-        validTexts.map(text => provider.getEmbeddings(text))
+      const embeddings = await withAiProviderFallback('embedding', config, (provider) =>
+        Promise.all(validTexts.map((text) => provider.getEmbeddings(text)))
       )
 
       return embeddings.map(embedding => ({