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/app/api/chat/route.ts

@@ -1,11 +1,14 @@
 import { streamText, UIMessage, stepCountIs } from 'ai'
-import { getChatProvider } from '@/lib/ai/factory'
+import { resolveAiRouteWithTiming, formatAiRouteDebug } from '@/lib/ai/router'
+import { runLaneWithBillingUser, willUseByokForLane } from '@/lib/ai/provider-for-user'
 import { getSystemConfig } from '@/lib/config'
 import { semanticSearchService } from '@/lib/ai/services/semantic-search.service'
 import { prisma } from '@/lib/prisma'
 import { auth } from '@/auth'
 import { loadTranslations, getTranslationValue, SupportedLanguage } from '@/lib/i18n'
 import { toolRegistry } from '@/lib/ai/tools'
+import { checkEntitlementOrThrow, QuotaExceededError, incrementUsageAsync } from '@/lib/entitlements'
+import { trackFeatureUsage } from '@/lib/usage-tracker'
 import { readFile } from 'fs/promises'
 import path from 'path'
 
@@ -46,6 +49,20 @@ export async function POST(req: Request) {
   }
   const userId = session.user.id
 
+  // 1.5 Quota check (per-provider BYOK bypass — only when BYOK will be used for resolved provider)
+  try {
+    const sysConfigEarly = await getSystemConfig()
+    const { usedByok: willUseByok } = await willUseByokForLane('chat', sysConfigEarly, userId)
+    if (!willUseByok) {
+      await checkEntitlementOrThrow(userId, 'chat')
+    }
+  } catch (err) {
+    if (err instanceof QuotaExceededError) {
+      return Response.json(err.toJSON(), { status: 402 })
+    }
+    console.error('[chat] Quota check error (fail-open):', err)
+  }
+
   // 2. Parse request body
   const body = await req.json()
   const { messages: rawMessages, conversationId, notebookId, language, webSearch, noteContext, format, noteId } = body as {
@@ -323,27 +340,43 @@ Focus ONLY on this note unless asked otherwise.`
 
   // 6. Execute stream
   const sysConfig = await getSystemConfig()
+
+  const routeDebug =
+    process.env.NODE_ENV !== 'production' || process.env.MEMENTO_AI_ROUTE_DEBUG === '1'
+  if (routeDebug) {
+    console.debug('[ai-route]', formatAiRouteDebug(resolveAiRouteWithTiming('chat', sysConfig)))
+  }
+
   const chatTools = noteContext
     ? toolRegistry.buildToolsForChat({ userId, config: sysConfig, webSearch, notebookId: notebookId || undefined })
     : toolRegistry.buildToolsForChat({ userId, config: sysConfig, webSearch, notebookId: notebookId || undefined })
 
-  const provider = getChatProvider(sysConfig)
-  const result = await streamText({
-    model: provider.getModel(),
-    system: systemPrompt,
-    messages: incomingMessages,
-    tools: chatTools,
-    stopWhen: stepCountIs(5),
-    onFinish: async (final) => {
-      const userContent = incomingMessages[incomingMessages.length - 1].content
-      await prisma.chatMessage.create({
-        data: { conversationId: conversation.id, role: 'user', content: userContent }
-      })
-      await prisma.chatMessage.create({
-        data: { conversationId: conversation.id, role: 'assistant', content: final.text }
-      })
-    }
-  })
+  const { result, usedByok } = await runLaneWithBillingUser(
+    'chat',
+    sysConfig,
+    userId,
+    async (provider) =>
+      streamText({
+        model: provider.getModel(),
+        system: systemPrompt,
+        messages: incomingMessages,
+        tools: chatTools,
+        stopWhen: stepCountIs(5),
+        onFinish: async (final) => {
+          const userContent = incomingMessages[incomingMessages.length - 1].content
+          await prisma.chatMessage.create({
+            data: { conversationId: conversation.id, role: 'user', content: userContent },
+          })
+          await prisma.chatMessage.create({
+            data: { conversationId: conversation.id, role: 'assistant', content: final.text },
+          })
+          if (!usedByok) {
+            trackFeatureUsage(userId, 'chat', final.usage?.totalTokens ?? 0)
+            incrementUsageAsync(userId, 'chat')
+          }
+        },
+      }),
+  )
 
   return result.toUIMessageStreamResponse()
 }