refactor(api): consolidate health check endpoints to /health

Removes the redundant `/healthz` and `/api/v1/health` endpoints, leaving `/health` as the sole health check endpoint.

- Update router to return 404 Not Found for the removed endpoints
- Update admin log filtering to only ignore `/health`
- Remove health URL from API documentation data
- Update tests to verify `/health` returns 200 and others return 404
- Update README documentation to reflect the change

backend/libs/services/bans.go

@@ -472,7 +472,7 @@ func (s *BanService) MaliciousPattern(path string) (string, error) {
 }
 
 func shouldSkipMaliciousPath(path string) bool {
-	return path == "/health" || path == "/healthz" || path == "/api/v1/health" || strings.HasPrefix(path, "/static/")
+	return path == "/health" || strings.HasPrefix(path, "/static/")
 }
 
 func (s *BanService) RecordAbuse(ip, kind, detail string, threshold int, now time.Time) (AbuseResult, error) {