Add missing explicit returns to 2 more functions

- stop_second_instance (line 1851) - Added return 0 before closing brace
- detect_recovery_level_from_errors (line 1076) - Added return 0 after echo

Both functions had no explicit return statements. While these don't cause
immediate exit-to-terminal like the step functions, they violate best practice
of always having explicit returns.

Severity: HIGH
Impact: Consistency and future-proofing

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

modules/backup/mysql-restore-to-sql.sh

@@ -1072,6 +1072,7 @@ detect_recovery_level_from_errors() {
     fi
 
     echo "$recommended_level|$error_type"
+    return 0
 }
 
 # Check error log for InnoDB startup issues (returns error type)
@@ -1847,6 +1848,7 @@ stop_second_instance() {
 
     # Mark as no longer running
     SECOND_INSTANCE_RUNNING=0
+    return 0
 }
 
 # Validate SQL dump integrity