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/api/ai/echo/fusion/route.ts

@@ -0,0 +1,107 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { auth } from '@/auth'
+import { getAIProvider } from '@/lib/ai/factory'
+import prisma from '@/lib/prisma'
+
+/**
+ * POST /api/ai/echo/fusion
+ * Generate intelligent fusion of multiple notes
+ */
+export async function POST(req: NextRequest) {
+  try {
+    const session = await auth()
+
+    if (!session?.user?.id) {
+      return NextResponse.json(
+        { error: 'Unauthorized' },
+        { status: 401 }
+      )
+    }
+
+    const body = await req.json()
+    const { noteIds, prompt } = body
+
+    if (!noteIds || !Array.isArray(noteIds) || noteIds.length < 2) {
+      return NextResponse.json(
+        { error: 'At least 2 note IDs are required' },
+        { status: 400 }
+      )
+    }
+
+    // Fetch the notes
+    const notes = await prisma.note.findMany({
+      where: {
+        id: { in: noteIds },
+        userId: session.user.id
+      },
+      select: {
+        id: true,
+        title: true,
+        content: true,
+        createdAt: true
+      }
+    })
+
+    if (notes.length !== noteIds.length) {
+      return NextResponse.json(
+        { error: 'Some notes not found or access denied' },
+        { status: 404 }
+      )
+    }
+
+    // Get AI provider
+    const config = await prisma.systemConfig.findFirst()
+    const provider = getAIProvider(config || undefined)
+
+    // Build fusion prompt
+    const notesDescriptions = notes.map((note, index) => {
+      return `Note ${index + 1}: "${note.title || 'Untitled'}"
+${note.content}`
+    }).join('\n\n')
+
+    const fusionPrompt = `You are an expert at synthesizing and merging information from multiple sources.
+
+TASK: Create a unified, well-structured note by intelligently combining the following notes.
+
+${prompt ? `ADDITIONAL INSTRUCTIONS: ${prompt}\n` : ''}
+
+NOTES TO MERGE:
+${notesDescriptions}
+
+REQUIREMENTS:
+1. Create a clear, descriptive title that captures the essence of all notes
+2. Merge and consolidate related information
+3. Remove duplicates while preserving unique details from each note
+4. Organize the content logically (use headers, bullet points, etc.)
+5. Maintain the important details and context from all notes
+6. Keep the tone and style consistent
+7. Use markdown formatting for better readability
+
+Output format:
+# [Fused Title]
+
+[Merged and organized content...]
+
+Begin:`
+
+    try {
+      const fusedContent = await provider.generateText(fusionPrompt)
+
+      return NextResponse.json({
+        fusedNote: fusedContent,
+        notesCount: notes.length
+      })
+    } catch (error) {
+      return NextResponse.json(
+        { error: 'Failed to generate fusion' },
+        { status: 500 }
+      )
+    }
+
+  } catch (error) {
+    return NextResponse.json(
+      { error: 'Failed to process fusion request' },
+      { status: 500 }
+    )
+  }
+}