refactor(backend): add status constants and update code to use them

- Create constants/statuses.js with MATCH_STATUS, SUGGESTION_STATUS
- Update routes/dashboard.js to use MATCH_STATUS
- Update routes/matches.js to use MATCH_STATUS
- Update routes/events.js to use SUGGESTION_STATUS
- Update services/matching.js to use SUGGESTION_STATUS
- Update tests to use constants

backend/src/routes/events.js

@@ -3,6 +3,7 @@ const { prisma } = require('../utils/db');
 const { authenticate } = require('../middleware/auth');
 const { getIO } = require('../socket');
 const matchingService = require('../services/matching');
+const { SUGGESTION_STATUS } = require('../constants');
 
 const router = express.Router();
 
@@ -1122,8 +1123,8 @@ router.post('/:slug/run-matching', authenticate, async (req, res, next) => {
     const count = await matchingService.saveMatchingResults(event.id, suggestions);
 
     // Get statistics
-    const notFoundCount = suggestions.filter(s => s.status === 'not_found').length;
-    const matchedCount = suggestions.filter(s => s.status === 'pending').length;
+    const notFoundCount = suggestions.filter(s => s.status === SUGGESTION_STATUS.NOT_FOUND).length;
+    const matchedCount = suggestions.filter(s => s.status === SUGGESTION_STATUS.PENDING).length;
 
     res.json({
       success: true,