feat: Complete internationalization and code cleanup

## Translation Files
- Add 11 new language files (es, de, pt, ru, zh, ja, ko, ar, hi, nl, pl)
- Add 100+ missing translation keys across all 15 languages
- New sections: notebook, pagination, ai.batchOrganization, ai.autoLabels
- Update nav section with workspace, quickAccess, myLibrary keys

## Component Updates
- Update 15+ components to use translation keys instead of hardcoded text
- Components: notebook dialogs, sidebar, header, note-input, ghost-tags, etc.
- Replace 80+ hardcoded English/French strings with t() calls
- Ensure consistent UI across all supported languages

## Code Quality
- Remove 77+ console.log statements from codebase
- Clean up API routes, components, hooks, and services
- Keep only essential error handling (no debugging logs)

## UI/UX Improvements
- Update Keep logo to yellow post-it style (from-yellow-400 to-amber-500)
- Change selection colors to #FEF3C6 (notebooks) and #EFB162 (nav items)
- Make "+" button permanently visible in notebooks section
- Fix grammar and syntax errors in multiple components

## Bug Fixes
- Fix JSON syntax errors in it.json, nl.json, pl.json, zh.json
- Fix syntax errors in notebook-suggestion-toast.tsx
- Fix syntax errors in use-auto-tagging.ts
- Fix syntax errors in paragraph-refactor.service.ts
- Fix duplicate "fusion" section in nl.json

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Ou une version plus courte si vous préférez :

feat(i18n): Add 15 languages, remove logs, update UI components

- Create 11 new translation files (es, de, pt, ru, zh, ja, ko, ar, hi, nl, pl)
- Add 100+ translation keys: notebook, pagination, AI features
- Update 15+ components to use translations (80+ strings)
- Remove 77+ console.log statements from codebase
- Fix JSON syntax errors in 4 translation files
- Fix component syntax errors (toast, hooks, services)
- Update logo to yellow post-it style
- Change selection colors (#FEF3C6, #EFB162)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

keep-notes/app/actions/profile.ts

@@ -98,3 +98,73 @@ export async function updateTheme(theme: string) {
     return { error: 'Failed to update theme' }
   }
 }
+
+export async function updateLanguage(language: string) {
+  const session = await auth()
+  if (!session?.user?.id) return { error: 'Unauthorized' }
+
+  try {
+    // Update or create UserAISettings with the preferred language
+    await prisma.userAISettings.upsert({
+      where: { userId: session.user.id },
+      create: {
+        userId: session.user.id,
+        preferredLanguage: language,
+      },
+      update: {
+        preferredLanguage: language,
+      },
+    })
+
+    // Note: The language will be applied on next page load
+    // The client component should handle updating localStorage and reloading
+    revalidatePath('/settings/profile')
+    return { success: true, language }
+  } catch (error) {
+    console.error('Failed to update language:', error)
+    return { error: 'Failed to update language' }
+  }
+}
+
+export async function updateFontSize(fontSize: string) {
+  const session = await auth()
+  if (!session?.user?.id) return { error: 'Unauthorized' }
+
+  try {
+    // Check if UserAISettings exists
+    const existing = await prisma.userAISettings.findUnique({
+      where: { userId: session.user.id }
+    })
+
+    let result
+    if (existing) {
+      // Update existing - only update fontSize field
+      result = await prisma.userAISettings.update({
+        where: { userId: session.user.id },
+        data: { fontSize: fontSize }
+      })
+      } else {
+      // Create new with all required fields
+      result = await prisma.userAISettings.create({
+        data: {
+          userId: session.user.id,
+          fontSize: fontSize,
+          // Set default values for required fields
+          titleSuggestions: true,
+          semanticSearch: true,
+          paragraphRefactor: true,
+          memoryEcho: true,
+          memoryEchoFrequency: 'daily',
+          aiProvider: 'auto',
+          preferredLanguage: 'auto'
+        }
+      })
+      }
+
+    revalidatePath('/settings/profile')
+    return { success: true, fontSize }
+  } catch (error) {
+    console.error('[updateFontSize] Failed to update font size:', error)
+    return { error: 'Failed to update font size' }
+  }
+}