Query entities from an Arkiv database chain using a filter expression. The filter uses a SQL-like syntax: comparisons (=, !=, <, >, <=, >=), logical operators (&& and ||), negation (!), and glob matching (~). Special attributes: $all (match everything), $owner (current owner address), $creator (original creator address, immutable), $key (entity key). Examples: '$all', 'status = "active"', 'score > 100', 'project = "myapp" && status = "active"', '$owner = "0x1234..."', 'name ~ "test*"'