Implement RLS and security functions

Apply Row Level Security to orphaned_images and system_alerts tables. Create RLS policies for admin/moderator access. Replace system_health view with get_system_health() function.

src/lib/integrationTests/suites/performanceTests.ts

@@ -220,7 +220,7 @@ export const performanceTestSuite: TestSuite = {
           const banStart = Date.now();
           const { data: isBanned, error: banError } = await supabase
             .rpc('is_user_banned', {
-              _user_id: userData.user.id
+              p_user_id: userData.user.id
             });
 
           const banDuration = Date.now() - banStart;