feat: add Claude proxy endpoint for auto pair generation

POST /api/claude/generate-pairs — proxies image + objects to Claude
Haiku and returns 30 structured pairs (text/yes_no/question, easy/medium)
as JSON. Keeps the Anthropic API key server-side via ANTHROPIC_API_KEY.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/index.js

@@ -40,6 +40,7 @@ app.use('/api/languages', auth, require('./routes/languages'));
 app.use('/api/user-names', auth, require('./routes/user-names'));
 app.use('/api/users-public', auth, require('./routes/users-public'));
 app.use('/api/users', auth, require('./routes/users'));
+app.use('/api/claude', auth, require('./routes/claude'));
 
 // 404
 app.use((req, res) => {