Bump version to 1.6.0

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Cargo.lock

@@ -2070,7 +2070,7 @@ dependencies = [
 
 [[package]]
 name = "image-api"
-version = "1.5.0"
+version = "1.6.0"
 dependencies = [
  "actix",
  "actix-cors",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "image-api"
-version = "1.5.0"
+version = "1.6.0"
 authors = ["Cameron Cordes <cameronc.dev@gmail.com>"]
 edition = "2024"