feat(models): add image model type support

Add a dedicated image model type so bots can use image API models without overloading chat model capabilities, while keeping existing chat-based image generation selectable.

db/migrations/0001_init.up.sql

@@ -92,7 +92,7 @@ CREATE TABLE IF NOT EXISTS models (
   created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
   updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
   CONSTRAINT models_provider_id_model_id_unique UNIQUE (provider_id, model_id),
-  CONSTRAINT models_type_check CHECK (type IN ('chat', 'embedding', 'speech'))
+  CONSTRAINT models_type_check CHECK (type IN ('chat', 'embedding', 'image', 'speech'))
 );
 
 CREATE TABLE IF NOT EXISTS model_variants (

db/migrations/0067_add_image_model_type.down.sql

@@ -0,0 +1,7 @@
+-- 0067_add_image_model_type (rollback)
+-- Remove image from the supported model types.
+ALTER TABLE models DROP CONSTRAINT IF EXISTS models_type_check;
+
+ALTER TABLE models
+  ADD CONSTRAINT models_type_check
+  CHECK (type IN ('chat', 'embedding', 'speech'));

db/migrations/0067_add_image_model_type.up.sql

@@ -0,0 +1,7 @@
+-- 0067_add_image_model_type
+-- Add image as a supported model type.
+ALTER TABLE models DROP CONSTRAINT IF EXISTS models_type_check;
+
+ALTER TABLE models
+  ADD CONSTRAINT models_type_check
+  CHECK (type IN ('chat', 'embedding', 'image', 'speech'));