docs(server): update open findings count to 6 after Medium batch

Resolved Server-003, -005, -007, -010, -011, -013 in this batch;
Server-004, -006, -008, -012, -014, -015 remain open (all Low severity).

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

code-reviews/Server/findings.md

@@ -7,7 +7,7 @@
 | Review date | 2026-05-22 |
 | Commit reviewed | `76d35d1` |
 | Status | Reviewed |
-| Open findings | 12 |
+| Open findings | 6 |
 
 ## Checklist coverage