feat: add OpenCode Go provider and support for custom models

- Introduced OpenCode Go provider with relevant configurations.
- Enhanced model management by allowing users to add and delete custom models.
- Updated UI components to support model selection for image types.
- Adjusted sidebar visibility to include image media kinds.

open-sse/services/model.js

@@ -13,6 +13,7 @@ const ALIAS_TO_PROVIDER_ID = {
   kmc: "kimi-coding",
   cl: "cline",
   oc: "opencode",
+  ocg: "opencode-go",
   // TTS providers
   el: "elevenlabs",
   // API Key providers