Code quality improvements from code review

- Add admin-only authorization for company and projects CRUD operations
- Create requireAccountId middleware to eliminate code duplication
- Standardize error handling (use next(error) consistently)
- Change error messages to Slovak language

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

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

src/middlewares/global/validateBody.js

@@ -13,7 +13,7 @@ export function validateBody(req, res, next) {
   for (const pattern of dangerousPatterns) {
     if (pattern.test(data)) {
       logger.warn('Suspicious input detected', { data: data.substring(0, 100) });
-      return res.status(400).json({ message: 'Malicious content detected in request data' });
+      return res.status(400).json({ message: 'Detegovaný škodlivý obsah v požiadavke' });
     }
   }
   next();

src/middlewares/security/requireAccountId.js

@@ -0,0 +1,20 @@
+/**
+ * Middleware na validáciu accountId parametra
+ * Kontroluje query alebo body a nastaví req.accountId
+ */
+export const requireAccountId = (req, res, next) => {
+  const accountId = req.query.accountId || req.body.accountId;
+
+  if (!accountId) {
+    return res.status(400).json({
+      success: false,
+      error: {
+        message: 'accountId je povinný parameter',
+        statusCode: 400,
+      },
+    });
+  }
+
+  req.accountId = accountId;
+  next();
+};