fix: Zero/negative chunk size guard

Added `MINIMUM_CHUNK_SIZE = 1` constant and `[..., MINIMUM_CHUNK_SIZE].max` to prevent infinite loop

Author: blocknotes

lib/active_storage/service/db_service.rb

@@ -18,8 +18,10 @@ class Service::DBService < Service
     end
     # :nocov:
 
+    MINIMUM_CHUNK_SIZE = 1
+
     def initialize(public: false, **)
-      @chunk_size = ENV.fetch("ASDB_CHUNK_SIZE") { 1.megabytes }.to_i
+      @chunk_size = [ENV.fetch("ASDB_CHUNK_SIZE") { 1.megabytes }.to_i, MINIMUM_CHUNK_SIZE].max
       @public = public
     end